Design of a feasible Corona wind air purifier to guarantee the capture and termination of hazardous fine bioaerosols for use in surgery and operation rooms in hospitals

(1)

tf

T

U

Delft

Technische Universiteit Delft

CPDNR3333

Conceputual Product Design

Process / Product System Engineering

Delft ChemTech

-

Faculty of

applied

Science

Delft uni

versity

of Technology

Final Report

Subject:

Design of a feasible Corona wind air purifier to guarantee

the capture and termination of hazardous fine bioaerosols

for use in surgery and operation rooms in hospitals

Author

Student Number

Telephone

Eliane Khoury

1207423

06-28129012

Keywords

Bioaerosols, HVAC (Heating, Ventilation Air Conditioning),

Operation room, Air Purifier, Corona discharge, Electric

(corona) wind, UV irradiation.

Assigment Issued

Report Issued

(2)

~

U

De

lft

Department of Biotechnology

Faculty of Apphed SCIence

,,~- : . " .... , .. . ' -. - . .

~-Wednesday, 22 March 2006 From: Pieter Swinkels

Appraisal Profile Conceptual Process or Product Design Project (CH3811) Theory & Concepts

problem analysis systematic approach Basis of Design AnalysisjEvaluation results Insight, understanding Implementation Independent team

Use of Group Process Tools (use list A+B to quantify) 1. StrengthjWeaknesses profiles

2. Extent of exploration outside 'normal' pattern (initiative) 3. Extent of 'over-time' (commitment)

4. ProjectjTime Management 5. Maintain Project overview

6. Handling of multi-culturaljmulti-discipline aspects (Ianguage, understanding, empathy, activity, participation

Use of Creativity Tools (use list A+B to quantify) 1. What methods were used, which notjwhy

• When were these methods uSed, frequency, how long • What was the result for the progress of the project 2. How manyjwhat kind of brain waves (booklet?)

• How many brain waves discussed, effect on project? 3. How is approach from team to these methods

Inventiveness, creativity Concrete Results Flexibility Communication Project progress Verba I presentation Formal reporting

Attitude during assessment meeting Remarks

Final Appraisal

(3)

:So/O"J(

ot

:.<>

~

L.J>

LO

-Lt

PAGE

/

1-

0

11

Problem not clearly defined (looks like technology push)

document Spellchecker not applied

t-. ~...,Jl2

...

e.

~ a..Vk..t1~ oz...~

11

Strenghts/weaknesses?

(/

-

c...-.1J)~

-

!.uil

_v/~è{

4 Does ozone formation also play a role in your designed product

5 Provide cost data for UV application

11

What particle si ze cut-off point is available for cyclones?

12 What air velocities are obtained by corona wind; is this sufficient to have

separation of smallest particles by centrifugation?

19 How did you take care of residence time distribution ?

20 Could you sketch an input/output diagram for the selected process

(kg/annum in/out and accumulated

in

device).

47 What is the mechanism by which contaminants are released at 1008

cfulm3 during operation?

47 What is the effect if the assumption of ideal air mixing in the operation

room is modified into partly plug flow and ideal mixing?

-What would be worse case (considering the location of the source of the

contaminants.

47

It

helps greatly ifyou structure the information needed into categories!

47 Dimensions of release rate S? cfulm31h?

49 Pressure drop?

58 What happens to the particles collected on the counter electrodes; will

accumulation lead to desfunctioning of the electrodes?

58 Will the corona centrifugal force lead to different residence times of air

and particles?

- -

tr-o

~

(f,el

(.

~

'

~

v

~{3~

-86

How was importance proven? Marketing analysis?

86 Mainly technical conclusions: what about market, economics, waste,

acceptance, patent

,

etc.

(4)

f!ti:.

U

··

Delft _____

c_o_nce_Pt_u_a_1 p_r_od_u_ct_O_e_s_i9_n_c_H_38_1_2 _ _ _ _ _ _ _

p

.

S~E

'

.'. .

TI

Final Report CPO - 3333

iilEtJ

Preface

Infectious diseases are among the scoops for nowadays research. A decent percentage of such diseases are caused by airborne pathogens. Therefore, a large variety have been developed for various applications, aiming to supply higher levels of air quality for purpose of comfort and health by reducing the concentration of such hazardous airborne pathogens, and hence the risks of infections.

However, the efficiencies of available technologies in capturing such bioaerosols are limited to relatively large particles; i.e. larger than 0.3 microns in size. This size range does not consider viruses, which are normally much smaller and lighter, especially the resistive viruses that can be transmitted in air for longer time than others, or use other small aerosols as a possible host during transmission.

Hospitals are type of facilities where high quality'Jf air should be achieved. That is since a large variety of diseases are gathered and concentrated in certain volume.

Furthermore, the patients are mostly immuno-compromised (has low immune system) due to diseases or during recovery after an operation.

Health reports concerning nosocomial (hospital related) indicate average infeetion rate of 10%; however, despite the fact that airborne organisms may not the major or the main source of contaminations or infection, high efficiency air purification may reduce the risk of infeetion per of 30-50 %.

These facts indicate the need for further air treatment in hospital, starting in operation rooms, where one is most vulnerable due to risks of infeetions through open wounds. Therefore, understanding the source and characteristics of the contaminants should be researched and determined, together with air related elements, such as ventilation system and existing air cleaning system. Based on these data, a highly efficient air purifier is required, and hence designed.

(5)

~; Conceptual Product Design CH3812 p~

T

U

Delft ______

F_in_al_R_ep_o--:rt_C_PD_-3_3_33 _ _ _ _ _ _ _ _

s

ËtJ

Summary

V'

v~

1 ~iA

s~

An inv~ti.Qè!iQ.npas been carried out to determine the technical and economical feaSffifiitY ofhigh efficiency air purifier by means of electrostatic forces created by the corona discharge phenomenon, in combination with Ultraviolet irradiation. Air purifiers are among the growing industries especially due to the increasing awareness of biological airborne threats, naturalor as terrorist act. Therefore, a lot of money is invested to design and manufacture efficient air purifiers that can çfàá'rantee safety and

health. ~

Su eh an air purifier is interesting due to the high efficiency it can supply in capturing small bioaerosols, which other air purifiers fail to catch due to their small particIe size. such high efficiency is required in order to reduce or eliminate the risk of infectious diseases, namely the airborne transmitted ones. Among the large possible markets for such an air purifier, the hospitals in the Netherlands were chosen to be the leader market. Hospitals normally have number of departments and therefore, use number of individual ventilation and air purification systems, where each system is adapted to work under different conditions based on the departments requirements and risk levels. Hence, in order to design an efficient system, the department and location specifications are to be determined. In this project, operation rooms were chosen to be the initial market. Where the designed product is designed to be set in a ventilation duct after the

existingjJi~ device named HEPA (High Efficiency Particulate Air filters) and before the air enters the operation room.

This project indicates that an electrostatic air purifier using the corona discharge

phenomenon is technically feasible. Evaluating various possible designs pointed out that air purifiers th at concentrate and eliminate hazardous bioaerosols (especially viruses, which tend to separate from their hosts on the impact with the filter) have the most potential for this application. The concentration acting is performed by applying high potentiaion sharp electrodes to created corona wind (ion ie wind), creating corona wind is used to manipulate the airflow pattern into circulation, where in addition to

electrostatic forces, centrifugal forces are applied on the particles and hence, get captured in the system. During this concentration process, high intensity of UV irradiation is applied within the use of medium pressure UV lamps, which cause the elimination of the targeted bioparticles (microbes).

An economie analysis is made from the consumer and manufacturer point of view. The equipments required for the system are~i.fi d are widely available, however, mostly costly. The estimated selling pri eper usin . approximately 10,000 Euros, which was found to be lower than the m ximum investment the consumer can afford while guaranteeing return on their investments within the product lifetime, which was estimated to be 10 years. The manufacturer profit from manufacturing su eh a product is dependent on the company strategies followed; however, it was proven that within the consideration of certain pricing strategies, the cumulative income might reach

(6)

If!.i..

Conceptual Product Design CH3812 p~

TU

Delft

______

F_in_a_1 R_e_po_rt_C_P_D_-_3_33_3 _ _ _ _ _ _ _ _

s

itJ

S

it)

.~

6.2.3. Side Effects ...

R. ...

67

6.3. VOLTAGE AND CURRENT REQUIRMENTS ... 67

6.4. UVGI LAMP ... 68

6.5. DATA INPUT and RESUL TS ... 70

7. TARGET SPECIFICATIONS (T.S.) ... 71 8. COST CALCULATION ... 73 8.1. INVESTMENTS ... 73 8.2. OPERATING COSTS ... 74 8.3. RETURN ON INVESTMENT ... 74 8.4. ECONOMIC CRITERIA ... 76

8.4.1. Rate Of Return (ROR) ... 77

8.4.2. Discount cash Flow Rate of Return (DCFRR) ... 77

9. ECONOMIC FEASIBILITY (P.P.R.) ... 80

9.1. MARKET SIZE ... 80

9.2. RETURN ON INVESTMENT ... 82

10. WASTE / SAFEl'Y ... 83

10.1. RISK ASSESSMENT ... 83

10.2. HAZARD AND OPERABILITY STUDY (HAZOP) ... 85

11. CONCLUSIONS AND RECOMMENDATIONS ... 86

11.1. CONCLUSIONS ... 86

11.2. RECOM~DATIONS ... 87

12. LIST OF SY~\LS ... 89

(8)

__________ C_O_"_oe __ P

t_u_a_l_pr_O_d_u_ct __ O_es_iQ_" __ C_H_3_8_12 __________________

P

.

S~E

· .'

..

Final Report CPO - 3333 ~Ëï:l

Table of Figures

Fiqure 2.1: The Product in its simplest form ... .7

Fiqure 2.2. Possible product functions and processes ... 8

Fiqure 2.3: Centrifugal Forces by Electrostatic Forces for ParticIe Concentration ... 12

Fiqure 2.4: UV Spectra I distribution (Relative energy versus wave length) for the UV lights B & C ... 14

Fiqure 2.5: Conceptual Scheme for the Product Concept and Location ... 15

Fiqure 3.1: Porter Five Forces Model for Hospitals ... 24

Fiqure 3.2. The OFD Process ... 29

Fiqure 4.1: ParticIe Distribution and Visibility in Air ... 34

Fiqure 4.2. The most penetrating biologica I agents for a HEPA filter ... 35

Fiqure 4.3: The Product functional concept.. ... 36

Fiqure 4.4: The conceptual choice scheme for the use of the designed product ... 37

Fiqure 4.5: Conceptual Scheme for the Product Concept and Location (Process Flow Schemel 38 Fiqure 4.6: Airflow Pattern (Laminar Down-flow) in Full Operation Room ... 40

Fiqure 4.7: Fundamental Block Scheme for the entire process when using 100% fresh air without recirculation, with HEPA efficiency of 99.97% and 5% of total particles smaller than 0.3 microns ... 49

Fiqure 5.1: Filed strength versus distance From discharge electrode [351 ... 53

Fiqure 5.2. Comparison of average UVGI rate constants for viruses, Bacteria and Spores [15, 351 ... 56

Fiqure 5.3: Specific Product Description for General Type of Operation ... 58

Fiqure 5.4: Corss sectional view for the product, where the active electrodes are connected to high potential power supply, while the passive electrodes are grounded needles (Ieft) or points (right) ... 59

Fiqure 6.1: Expected Airflow profile versus electrodes configuration ... 65

Fiqure 6.2. Corona Wind Velocity versus electrodes angle ... 65

Fiqure 6.3: Corona Wind cvclone due to mixed polarities ... 66

Fiqure 8.1: Cash Flow Diagram for estimating the pay back (oID time ... 78

Fiqure 8.2. Cash Flow Diagram for the calculation of the maximum possible investment.. ... 78

Fiqure 9.1: Location of all hospita Is in the Netherlands ... 80

Fiqure 9.2. Diffusion Curve of the Designed Product in the Netherlands ... 81

Fiqure 9.3: Cash flow based on constant unit-selling price of 10000 Euros ... 82

(9)

fu

Delft _____

co_n_ce_F_~t_:a_~_I:_;_:_:rt_uct_c_~_~_~i_~_~_;3_H_38_1_2

_ _ _ _ _ _ _ _

p~

1. INTRODUCTION

Project organization and objectives

The principal of this conceptual produet design is Prof. Dr. Ir. Peter Appel. Together with the designer, the broad interest in the project is the question whether an air purifier to be used in hospita Is for capturing hazardous bioaerosols, mainly viruses, reducing or eliminating the infections resulted by them is technically feasible and commercially competitive. The project is technically supervised by Prof. Dr. Ir. Peter Appel and Ir. P.L.]. Swinkels, who is as weil the assigned creativity coach.

In a hospital environment, there tend to be high concentrations of harmful

microorganisms. Such microorganisms are called pathogens and may cause infectious diseases, which are among the major concerns of hospitalised patients and hospita Is staff. Pathogens have several transmission routes, among them the airborne

transmission. Airborne pathogens include large variety of microorganisms such as bacteria, fungi and viruses, etc, which differ is charaeteristic, size and health impact. Therefore, in hospitals environment they are particularly dangerous because of reduced immunity levels in patients.

The risk of being infected due to the airborne route of pathogens transmission is a function of particIe concentration. The chance of aparticle that is carrying an organism falling into an open wound or inhaled into the lungs increases with particIe

concentration. Thus, by reducing the concentration we reduce the chance of infection and, hence, the number of patients infeeted. For this purpose ventilation systems in hospitals are designed to reduced to concentration of such particles, in additions to the thermal and humidity comfort, by diluting the indoor environments with fresh air. In addition to the ventilation system, air purification systems, such as high efficiency micro-porous filters, are set in the ventilation duet to capture the other particles and reduce their possible concentration in the indoor space. However, such filters are mostly geometric and therefore, they have efficiency limitation due to particIe size distribution (the characteristics of such filters are explained further in addition to appendix 1).

The difference in bioparticles' sizes forms the main objective for the project. That is since relatively small particles, i.e. less than 0.3 microns are hardly captured by available technologies. Among these small bioaerosols are viruses, mainly the resistive viruses that can be transmitted in air for longer time than others, or use other small aerosols as a possible host during transmission.

(10)

~. Conceptual Product Design CH3812 p~

T

U

Delft ______

Fin_a_1 R_e_p_ort_CP_D_-_3_33_3 _ _ _ _ _ _ _ _

s

El)

The question is which methods are suitable for capturing and eliminating the viruses and the other small particles and what is the acceptable threshold for such contaminant. Should they be concentrated and collected only or also eliminated, if yes then how. Should combined processes take place at the same time, or divide the total system into segments. And what are the required forces to achieve such particIe separation from the air stream and supply safe environment.

Air purifiers

In principle, air cleaners may be a part of a ventilation system, or an external-individual system. However, due to the variety of contaminants present in the air, such as smoke, duct, pollens, bacteria, viruses, etc, there is a large variety of air cleaners type, which are designed under different specifications. Furthermore, due the differences in chemical and physical properties of the contaminant present in the air, available air purifiers cannot adequately remove all of the pollutants typically found in indoor air.

The choice for the adequate air cleaner depends on several elements: type of ventilation system (fresh air or circulated); the location (c1eanliness of air in the area); occupancy (number of people in the facility); type of facility (office, school, home, industrial plant, hospital, etc.); contaminants source and occurrence conditions; quality level required; etc. Based on similar considerations it is logical to conclude that air cleaners that have high filtrating or purification efficiency and are designed to handle large amounts of air are the best choice for use in buildings with high number of occupants such as :office buildings and hospitais.

Hence, air purifiers may be designed or used to capture variety of indoor environment contaminants, as mentioned earlier: [1]

• Inorganic contaminants, such as, Carbon dioxide, Carbon monoxide, Nitrogen dioxide, Sulphur dioxide and Ozone,

• Organic contaminants, such as, Volatile organic compounds, Formaldehydes, Pesticides, Polynuclear aromatic hydrocarbons and Polychlorinated biphenyls. • Physical contaminants, such as, Particulate matter, Asbestos, Man-made mineral

fibers and Radon.

• Environmental Tobacco Smoke.

• Biological contaminants, such as, House dust, Dander from furred animals (pets), Pollen, Fungi, Bacteria and viruses, etc.

Therefore, each has different typical concentration and exposure level, which cause different health effect and impact. Due to theses differences, air purifiers from each contamination agents should be designed differently where all the differences are taken into account, and integrated into the indoor environment without unbalancing its nature.

(11)

_________

c_o_n_c_e_~_u_al_IP_r_o_du_ct

Fma Report CPD - 3333 __ D_e_Si_g_n_C_H_38_1_2 _______________

P_

.

S~E

"'Ël)

.

..

.

Current developments

Over the last twenty years the terms MCS Multiple Chemica I Sensitivity and ETS -Environmental Tobacco Smoke have become an integral part of air filtration j

purification technology. Early filtrations focused on removing toxic chemica Is, noxious gases, and foul orders, but were unable to remove airborne microorganisms. While more modern filtration devices focused on removing mold spores, viruses, and bacteria from air. [2]

The need for the air purification devices has expanded over the years to include

protection against fabric chemica Is, perfumes, building materiais, pesticides, dust mites, pollen, and food odors, etc. Furthermore, the outbreaks of the Ebola plague in Africa showed how important it truly was to be able to re move hazardous bacteria from the air by purifying it. This brought on the new generation of air cleaners and air filters. [3]

Today there is a large selection of air purifiers to choose from for home use, offices, hospitais, industry and others, with variety of efficiency ranges. It all depends on what the consumers' personal needs are, whether it is just allergies, bacteria, viruses, or maybe just supplying fresh air. Air cleaners are generally classified according to the technology employed to re move various sized particles andjor gases from the air. The selection of a type of air filter should depend on the intended use of the filter. Air filters' wide applications include:

1) Protecting the HVAC equipment and components. 2) Protecting the furnishings and decor of occupied spaces. 3) Reducing housekeeping and building maintenance. 4) Reducing furnace and heating equipment fire hazards. 5) Protecting the general well-being of residents.

The first four of these applications can be accomplished with the lower efficiency filters generally used in central HVAC systems. The last, which has to do with health issues, will require much higher performance filtration. It may not always be possible to install this equipment in ol der existing environmental systems. Thus, self-contained portable room air cleaners must sometimes be used to obtain sufficiently high levels of filtration effectiveness [4].

Air cleaners include the simple furnace filter (for furnace or central air conditioning in a facility such homes or office that uses an air filter), the electron ic air cleaner, and the ion generator. Mechanical filters (retention of particles on filter media by direct interception) either flat or pleated are generally effective at removing particles. Their efficiencies relate to their nominalor absolute pores size. They are also very affected by processing conditions, such as operating velocity, pressure, and concentration of

(12)

Conceptua' Product Design CH3812 p~

_ _ _ _ _ _ _ F_i_na_'_R_e_po_rt_C_P_D_-_3_33_3 _ _ _ _ _ _ _ _ _ _

S

ËtJ

Electronic air cleaners and ion generators use an electronic charge to remove airborne particles; these devices mayalso produce ozone, which is considered as hazardous byproduct, and may cause lung irritation, and therefore is not desired. All air cleaners require periodic cleaning and filter replacement to function properly. Other electron ic air cleaners intentionally produce ozone, and therefore, called ozone generators, which are believed to create ozone, which disinfect the bacteria and decompose back to oxygen. See appendix 1.1 for further details on mechanical filters.

In addition to removing particles, some air cleaners may re move gaseous pollutants; this is possible only if the air cleaner contains special material, such as activated charcoal, to facilitate removal of harmful gases. Although some of the devices designed to remove gaseous pollutants may be effective in removing specific pollutants from indoor air, none are expected to adequately re move all of the gaseous pollutants typically present in indoor air. Information is limited on the useful lifetime of these systems; they can be expensive and require frequent replacement of the filter media.

Furthermore, there have been innovations on activated carbon filters th at have been able to fit into smaller units for homes and businesses. The activated carbon filters contain pounds of activated carbon that is designed to trap and hold odours, toxic chemica

I

fumes and noxious gases.

Among the very large variety of available filtration and air cleaning methods, an emphasize for hospitals applications is drawn towards the HEPA filters, UV (Ultraviolet) irradiation, which will be explained in details further and Positive pressure in the rooms.

New HEPA filtrations consider combination of technologies to assure higher efficiency in

contaminants collection or elimination. Such efforts may take the form of designing higher surface of the filters; design of polymer based media filters, which allows higher airflow and thus requires a smaller, less noisy fan. The trick in these air purifiers is the addition of electrostatic brushes in the airflow prior to the HEPA element. This charges the pollution particles and gets them to "stick" electronically to the filter media. [4]

UV (ultraviolet germicidal irradiation) light is known to be very effective in killing many germs, mold, bacteria, and viruses. They initiate a photochemical reaction th at affects the DNA of the microorganisms and prevents their growth. Therefore, a large variety of products and technologies are investing in developments of new systems th at can profit and benefit from the UV abilities. [6]

That, in short, indicates the possibility as weil as the need for combining technologies and to improve available ones. Such combinations may turn air purifiers to

multifunctional devices and increase their efficiency by combining advantages of different types of air purification methods in one device.

From the large variety of technologies and developments, I see any combination of existent filtration system with electrostatic (charging) precipitation or the use of UV lamps as major competitors. Examples of such competing technologies are:

(13)

!!J!i..

.

Conceptual Product Design CH3812 p. S~E. ... .

T

U Delft ______

Fi_na_I_R_ep_o_rt_C_P_D_-_33_3_3 _ _ _ _ _ _ _ _ _

"ë'tJ

• The Ultraviolet lamps individually: the additions of UV lamps in the air duct or in

the facility in general can be very effective, however, 50 far the major downside ( ')

0-,:

for such method is the high costs: product and operating costs. _

~

Ir

1

• The combination of HEPA with UV light: caught particles may be eliminated

+

~

GR)

-within the use of UV before they penetrate through the HEPA.

• The combination of HEPA with electrostatic precipitation by using air charger, mainly before the HEPA phase, to help stick particles on the filter.

See appendix 1 for further detailed description of air cleaners processes.

Project outline

This project has a lot of degrees of freedom. The project was allowed to choose varia bie such as the product category, market, target specifications, technology used and

operation conditions. After long literature research, a decision was made to consider an air purifier for the use in the air supply pipeline for operation rooms in hospitais, mainly in the Netherlands as the target market.

(14)

I!!:!!..

'

T

U

Delft ______

F_in_a_1 R_e_p_ort_CP_D_-_3_33_3 _ _ _ _ _ _ _ _

s

itJ

2. PROCESS OPTION AND SELECTION

This chapter describes the route of the "best" design. A literature study and creative input from the designer and the supervisors, revealed various alternatives for the

problem approach and solution design. Based on criteria, which were set in advance, the best design was determined with the information present at th at time. The result of the product options and selection is the product th at is seen as the most optimal and most promising and therefore, it is worked in detail. The design level achieved in this chapter is on the level of functions. These functions are translated into equipment in further chapters.

2.1. DESIGN CRITERIA

Before evaluating possible options for the design or possible designs in genera I, the criteria that the design needs to meet should be discussed. These criteria have been set based on consumers needs and designers' considerations; and therefore organized in several categories rated from most to least important, in order to construct an overall rating for the design. These categories are displayed in Table 2.1. However, they are rated in next chapters when constructing the house of quality for the suggested product. Note that each criterion can prohibit the design from being accepted. For instance, unsafe aspects of a design can obviously not be compensated by a small equipment size or a low maintenance frequency.

Table 2.1: Criteria for the ueSICJln

Small Size

Electrical Efficiency Low capital Costs Availability

Allows the system to be applied more easily in an

",victirln ventilation C\'c:1""'rYI

Good for economics and better electricity to heat ratio

Determines up to a large extent the profitability of

the n

Easily supplied and adjusted to available space dimensions

(15)

Conceptual Product Design CH3812 P~.

.

Final Report CPD - 3333

- - - E

In addition to the design the consumer needs, the design must be valid regarding the rules and legislation, national or international, based on the market chosen. Among the few data available concerning contaminant concentration threshold in operation rooms, some rules were found and are presented as follows [61]:

The empty operation theatre shou/d have:

(a) Less than 35 colony-forming units (CFU) of bacteria per m3 of air.

(b) Less than one CFU of Clostridium perfingens or Staphylococcus aureus in 30

m

3

.

Durinq operation the theatre shou/d have:

(c) Less than

180

CFU/ m3 of air using ultra clean laminar flow in the theatre. (d) Less than

20

CFU/ m3 at the periphery of the enclosure and less than

10

CFU/ m3 at the centre.

2.2. PRODUCT OPTIONS

The most general definition of the product is: the design of an air cleaner that captures the small bioaerosols in the air stream before entering the operation room. Figure 2.1 presents the simplest schematic for this product.

Contaminated

air ..

...

Air Cleaner:

Bioaerosols

Capture

Fiqure 2.1: The Product in its simplest farm

Purified air

..

...

(16)

Conceptual Product Design CH3812 p~ Final Report CPD - 3333 _ _ _ _ _ _ _ _ _ _ _ _ " SE" """ "

Bioaerosols

Count/m'

,---

--- -

~----

--- ---- ---- ---

-

--- ---- -- -- --

---Feed

~~~~

Monitoring

~

....

~~I

Collection

~1

....

~~I8illUnation I~

...

(C

Fiqure 2.2. Possible product functions and processes

Part of the possible functions presented in figure 2.1 is optional, and as mentioned above, the final product may contain one or more of these functions (see appendix 2.1 for possible combination between the possible functions). However, it is important to emphasize the choices of necessary or optional function.

In order to identify the necessity of each stage and in order to choose the functions of the designed product, several options were considered for each stage. These options are presented and elaborated for each stage considered. The pros and cons of the options will be mentioned. Some options will be discarded at once; other potential options will be evaluated in the next stage of evaluation. In this second stage all possible

combination of the options are evaluated while taking into account the influence of the individual function on the complete design.

2.2.1.

Monitoring The Bioaerosols Count

Monitoring the bioaerosols in the air can be performed online (real time) or offiine. And thus there is a large variety of monitoring devices, however, the majority of such systems are designed for the purpose of research. For the designed product, if considering monitoring system, an online monitoring is desired.

Most effective online monitoring system for bioaerosols is the UV-APS (Ultraviolet Aerodynamic ParticIe Sizer), which had been used during the first Gulf war; however, false signals were obtained, which indicates low reliability of the results [7, 8, 9]. Furthermore, it is used to Characterizes individual airborne particles between 0.5 to 15 IJm [10], which are larger than the considered particles for the designed system. Other available system is the "Slit-Type Volumetrie Spore trap (STVS), which is

considered reliable for sampling fungal diseases in Eucalyptus globulus plantations [11]. However, it is efficient for spore particles, and does not consider smaller bioaerosols.

(17)

fu

Delft _____

c_o_n_ce_~_i~u_aa_IIR_Pe_r:_:_~ct_c_~_~_~i_~_~_~3_H_38_1_2

_ _ _ _ _ _ _ _

p~

Additional aerosols monitoring system mayalso be considered, such as Scanning Mobility ParticIe Sizer (SMPS) [12], or Differential Mobility Analyzer (DMA) [13], which separates particles based on their electrical mobility.

However, to evaluate the need for such system in the designed product or this project, the consumers need and manufacturer capabilities are to be taken into account. Hence, the monitoring stage, from consumer' point of view, may be required for convenience as an indication th at the system works effectively by measuring air composition before and after the product and indicating the reduction in contaminants concentrations. In other words, a monitoring system can supply higher reliability indication for the consumer by detecting the existence of harmful bioaerosols in the specific room or its cleanliness. However, for the design purpose, such a system is not required for the performance of the product; hence, it would be cheaper and easier to perform such tests in the testing phases in the manufacturer laboratories and after the installation of the system. Therefore, it is not required to be part of the installed system in the consumers' facilities.

Furthermore, from manufacturer point of view, there are number of systems available in the market for monitoring and therefore, competing with such technologies while complicating the suggested system in the chosen market, which was shown to have a moderate potential, would not be a good idea, especially when considering price. When evaluating the need for the monitoring system from the designer point of view, similar considerations are to be taken into account. And, as mentioned earlier, it is important to identify the necessary or the optional functions of the system.

Thus, since the purpose of the product is reducing the bioaerosols from air, it is obvious that the reduction may be performed by their collection or elimination of the

combination of both functions, therefore, these two functions are considered as relatively necessary. However, The monitoring stage may be considered as additional function, which is meant mainly for convenience and control, and does not contribute to the efficiency.

Furthermore, since the designed product is meant for the protection and purification of operation rooms, which in definition are suppose to be ready for use all the time, the product is to be functioning continuously; Therefore, the monitoring stage is optional. Based on all mentioned above, no monitoring system was considered further in the design.

2.2.2.

Collection of Bioaerosols

As mentioned earlier in the project objectives, the designed system aims to collect and capture the bioaerosols th at penetrate through the existing filtrations, such as viruses and small bacteria. Therefore, Due to the "non-total" filtration efficiency of the existent filtration systems used, HEPA filters (99.97% down to particIe of 0.3 microns in

(18)

JItii

.

T

U

Delft ______

F_in_al_R_ep_o_rt_C_PD_-3_3_33 _ _ _ _ _ _ _ _ .

SEtJ

theatre (from the wound, skin and surfaces due physical movements and aerodynamic effects), especially the airborne pathogens, further developments should be performed.

Microbial agents are known to be small in size; bacteria are known to have si ze distribution range from few fractions of microns (about 0.8 microns) up to 50 microns [14]. However, some airborne bacteria are even smaller, such as Chlamydia pneumoniae (0.3 microns) and Bordetella perlussis and Mycoplasma pneumonia (0.25 microns); Appendix 6 presents a detailed description of considered microorganisms.

Such microorganisms are not expected to be captured by the available filters such as the HEPA filters. Due to such contaminants, operation rooms are mostly supplied by

ventilation systems that supply continuous dilution of the indoor air by 15- 25 % fresh air or even use 100% fresh air, which is believed to be safer and more sterilized than indoors air [15].

Hence, it is obvious that the concentration of such contaminants suspended in the air may be very low. However, despite their low concentration, they still form a threat on the health of the population in the operation theatre: staff, patients, etc.

Therefore, to successfully and efficiently capture such contaminant, a concentration process is enhanced and may be considered very essential. Within this process, the concentration of suspended particles in air, aerosols and bioaerosols, is reduced, while collecting these agents in the concentrator.

Furthermore, since the designed product may aim and consider the elimination of such hazardous agents, the concentration process may guarantee intensive and efficient elimination of the agents by supplying higher time distribution in the system, while increases their exposure time to the elimination source.

Based on these requirements, the concentrator must have a relatively high efficiency, or ability to collect the appropriate sized particles from a given volume of air.

One technique to concentrate airborne particles is to separate the small and large particles. Several methods for spreading aerosols particles are available. Some, such as bubblers or impingers, involved submerging the particles in a liquid. However, this project considers dry particIe and separation in order not to affect the humidity level or supply further suspended liquid droplets in the air, which may act as a host or a carrier for microorganisms [16, 17]. Currently various equipments and instruments such as cyclones, centrifuges, optical counters, differential mobility analyser, filters and inertia impactors are available for measuring or classifying particles [18]. The two mostly commonly used dry particIe separation devices are impactors and cyclones.

Impactors,

mainly classify particles in the size range of 0.1 - 20 microns. Due to dimple design rugged structure and easy operation, the impactor is considered one of the most popular piece of aerosol instrument equipment. Impactors are based on the principle th at when airflow changes direction suddenly, relatively large particles continue moving forwards due to their inertia, while small tend to follow curved air stream lines.

(19)

Conceptual Product Design CH3812 p.~.

.

Final Report CPD - 3333

- - - E·

By designing properly geometric parameters such as inlet diameter, diameter of the flow acceleration nozzle diameter of impaction plates, the distance between the flow

acceleration nozzle and the impaction plate, large particles can be separated from small particles with low internalloss. (See appendix 2.2 for further information about impactor types).

Cyclones

are collection systems where particles are removed by causing the entire gas stream to spin in a vortex at high velocity inside a cylindrical chamber. The centrifugal force acts more strongly on the larger, denser particles and flings them preferentially toward the inside wall of the cyclone where they impact and then fall to the bottom of the cyclone. The gas flows out through the top of the cyclone (still carrying some of the smaller, lighter particles), while the collected dust is removed from the bottom [20].

Cyclones are used as particles separators, but by extracting a minor flow of the

concentrated particles, they become concentrators. A number of different cyclones types are available such as: straight through, reverse flow (conventional) [21, 22]

OU5tool

Typically, a particulate-Iaden gas enters tangentially near the top of the cyclone, as shown schematically in the figure. The gas flow is forced into a downward spiral simply because of the cyclone's shape and the tangential entry. Another type of cyclone (a vaneaxial cyclone - see right panel of the figure) employs an axial inlet with fixed turning vanes to achieve a spiraling flow. Centrifugal force and inertia cause the particles to move outward, collide with the outer wall, and then slide downward to the bottom of the device. Near the bottom of the cyclone, the gas reverses its downward spiral and moves upward in a smaller inner spiral. The cleaned gas exits from the top through a "vortexfinder" tube, and the particles exit from the bottom of the cyclone through a pipe sealed bya spring-loaded flapper valve or rotary valve [50]. (See appendix 2.3 for further details).

In addition to such mechanical concentrator, a revolutionary electrical concentrator may also be considered. Such concentrators are still in the research phase and are not applicable yet, however, the familiar forms of such methods are the electronic gas or air cleaner as explained earlier. On example of this these forms is the electrostatic

precipitation.

(20)

~. Conceptual Product Design CH3812 p~

T

U Delft ______

F_in_a_1 R_e_p_ort_CP_D_-_3_33_3 _ _ _ _ _ _ _ _

s

itJ

typically results in high collection efficiency with a very low air pressure drop [20, 22, 23] (See appendix 2.4 for further details).

Hence, since the ESP collected particles on its plates, it may be considered as particles concentrator as required for the design. However, an additional electric particIe

concentrator, from the revolutionary designed category, is the use of electric forces and electric wind created from the discharge electrodes to combine the characteristic of the ESP and the cyclones or Centrifuges. This form of concentrator may be ca lied : corona wind cyclone, based on the corona wind phenomenon discussed in large number of literature and researches (see appendix 2.5-2.7 for corona discharge and wind properties) .

A brief description for such cyclon~ is as mentioned above, the combination between electric and centrifugal forces. That is possibly do ne due to the fact that when using sharp electrodes under high potential, a phenomenon called corona discharge is

obtained, which is a very high electric field on the tip of the sharp electrode, causing air ionisation. The ionised particles and molecules drift away in the direction of the electric field, causing electron avalanche (appendix 2.6), which results in what is knowas the electric wind [24-27]. With proper design of electrode geometry the electric wind may be combined from several discharge electrodes to cause manipulation of the air stream(

causing centrifugal profile, which in turn affects the particles and collect them to the inner wall of the created cyclone, as presented in the following figure.

~

~v-~

~J

,

GA

[j)~

Fiqure 2.3: Centrifugal Forces by Electrostatic Forces for ParticIe Concentration

(21)

~. Conceptual Product Design CH3812 p~

TU Delft ______

F_in_a_1 R_e_po_rt_C_P_D_-3_3_33 _ _ _ _ _ _ _ _

s

EtJ

The choice of constructing such may be based on comparison of efficiencies between the three concentrators mentioned above, which is performed later in the evaluation section. Therefore, no detailed description of the corona wind cyclone is valid for this stage.

2.2.3.

Elimination of Bioaerosols

Elimination is possible by using chemical disinfector. An example for chemica

I

disinfection and Inactivation of the foot and mouth virus consist of: sodium hydroxide (2%), sodium carbonate (4%), and citric acid (0.2%). Resistant to iodophores,

quaternary ammonium compounds, hypoclorite and phenol, especially in the presence of organic matter [40].

Other viruses are sensitive to other substitutes. That indicates that the requirement for composing chemical disinfectors for the large variety of viruses may be complicated. Furthermore, such compounds may require long time to decompose, which is an undesired result, therefore, the chemica

I

disinfection was not considered an option unless for an internal use in the system.

Ozone is known to be astrong oxidizer that kills microorganisms effectively at physically contact with the pollutants, odours, germs and viruses' particles. It breaks them down, disinfect the air and turn back to a stabie molecule of oxygen [41]. However, the use of a chamber of ozone is not an option due to the insecurity of the system, the risk of ozone leakage to the room space and the low efficiency expected due to short time of contact, especially since an outlet for the purified air must exist. This can be an option only when setting a nano membrane at the end to guarantee non-exit of the biological agents or ozone molecules back to the air. However, the first guess would be high production costs, which decrease the chance of merging in the market. Furthermore, legislations and validations should be checked, mainly due to the use of ozone in sensitive facility such as hospital.

Electrically shocking the viruses may be an option to eliminate them. That is done by stripping their electron and neutralizing their electrical charge, which deactivate them. Most bioaerosols seem to be generally partially negatively charged [35]; therefore shocking them with positive potential similarly to electrical precipitation may achieve this requirement. In other words, this is one of the options that may occur when using the corona principle or ESP.

Collection on a poisonous medium is an option, however, here we run the risk of

(22)

_ _ _ _ _ _ _ F_in_a_I_R_e_po_rt_C_PD_-_33_3_3 _ _ _ _ _ _ _ _ _ _

S

Ët)

Ultraviolet Irradiation is used in air and water disinfection. It is known to be effective be effective in killing biological contaminants such as mold/fungi, bacteria and viruses. For

air disinfections, lamps are typically placed inside air handling ducts, mobile room air cleaning units and in special fixtures mounted toward the ceiling in rooms. Among the most common applications are in hospita

I

for the use in the laboratories and for water disinfections [42]. The process is known as simpie, reliable, economical and is employed either as a stand-alone solution or in combination with other methods such as filters, ozone and chemicals [43-45].

The disinfection process and treatment occurs when UV initiates a photochemical reaction, which effectively damages the DNA (deoxyribonucleic acid) molecule to such an extent th at cell division (breaks the C=C bond), and thus multiplication, can no longer occur due to cellular death [16].

Through research, biologists determined the amount of UV required to destroy different kinds of microorganisms. This amount of UV is referred to as the "dosage", which is determined based on the intensity of the UV (expressed in microwatts) th at is delivered for a given period of time (seconds), over a given area (square centimetres).

Power X Time X Area or microwatts-sec/cm2 (JlW-sec/cm2)

The relative effectiveness of UV light wavelengths for the process is known as the germicidal action spectrum, and it is dependent on the type of microorganisms required

to eliminate, which vary in their structure and hence the sensitivity to UV-C

irradiation. The germicidal effect of the UV-Cis obtained at wavelength of almost 254 nanometers (for most ozone-free air purification applications) [46-49] and thus called UVGI (Ultraviolet germicidal

irradiation). (See appendix 2.8 for further information and for choice justification). However, despite the fact the germicidal effect of the UV fall between the B and UV-C, the UC-V is best choice based on characteristic and their impact on health (UV-C includes ozone generation). In addition to th is, when comparing UV Spectra

I

distribution for these different UV types, best results energies are obtained for the Uv-c.

UV-c Germiddal UV-B

i Puk: 2n.7n.m Puk: '06nm

Fiqure 2.4: UV Spectral distribution (Relative energy versus wave length) for the UV lights B & C

(23)

fu

Delft _____

c_o_n_c_eF_~t_:a_~_I:_:_;o_d~_ct_c_~_~_~i_~_~3_c3_H_38_1_2

_ _ _ _ _ _ _ _

p~

2.3. POSSIBLE ALTERNATIVES EVALUATIONS

In principle, the system is designed to be set in the ventilation duet, after the existent filtration system and before the air entrance into the room as shown in the following figure. This order is set based on the design target to focus on capturing particles, which succeed to penetrate though the existing filtrations.

sh Fre

(outdo or) air

..

HVAC

...

Indoor air (In case of Indoor air recycle)

Existent

Filtration

New

Purification

Fiqure 2.5: Conceptual Scheme for the Product Concept and Location

Clean Air

..

...

However, due to the variety of ventilation system's types, different capacity of the ventilation systems may be considered. For example, it could be centra I system, supplying air for the who Ie hospital, or central for one departments or local for certain rooms. Generally, the ventilation systems for operation rooms are local, serve only the operation room or series of the operation rooms, this is elaborates in further chapters.

When considering the difference in ventilation system capacities; the different options of existenee pre-treatment (HEPA filter) of the air before the entering the designed system and the individual funetions of the product as expressed earlier (monitoring, Colleetion and elimination), various combination may be constructed (see appendix 2.9 for

construeted combination). When rating the possible combinations of all these elements, it was obvious th at first priority was considered for total system designed for operation rooms th at is supplied with air through alocal ventilation system, with pre-filtration (existent filtration (HEPA)) together with the designed system while containing all three suggested functions: monitoring, collection and elimination. Therefore, the design conditions are chosen based on these results and as shown above in figure 2.5.

(24)

_ _ _ _ _ _ _ F_in_a_I_R_e_po_rt_C_PD_-_3_33_3 _ _ _ _ _ _ _ _ _ _

S

Ëtl

2.3.1.

Concentrator Evaluation

Impactors

are very efficient for concentration and separation of big particles> 1 micron and much smaller than that, however, in the zone of 1 micron particles, the impactor has a very low cut off size and low efficiency, due to low mobility of particles at th at size. And since bacteria and dust particles, which can carry viruses with them may be in the zone of 1 micron, and they still may penetrate through the existent filtration system used (such as the HEPA with efficiency of 99.7-99.97%), a relatively low efficiency would be expected within the use of an impactor [16, 19 (NAllBO)]

Cyclones: just like any other device, have their advantages and disadvantages.

Advantages of cyclones are th at they are simpie, rugged, and inexpensive. Also, they collect the PM in a dry form 50 that it can be re-used or recycled (in industrial

applications). The major disadvantage is that the collection efficiency tends to be somewhat low. In fa ct, the efficiency of a cyclone is often too low to be able to use the cyclone as a final control device. Therefore, cyclones are often used as pre-cleaners. Furthermore, moving the gas through a cyclone at high enough veloeities to collect a reasonable fraction of the PM, creates a substantial pressure drop (which means an increase in operating costs) [31].

Further more, Cyclones by themselves are generally not adequate to meet stringent air pollution regulations, but they serve an important purpose. Their low capital cost and their maintenance-free operation make them ideal for use as pre-cleaners for more expensive final control devices such as baghouses or electrostatic precipitators [50]. When comparing cyclones vs. impactor, no absolute winner can be found, however, based on the comparison in details in appendix 2.10, and in the table bel ow, cyclone may have higher benefits for collection of the desired particles based on size.

When considering particIe concentrator, the determining factor for the optimal

instrument choice is primarily particIe concentration, and secondarily particIe size.

And since the designed product considers collecting small particles with low

concentration, it is obvious that cyclones and impactors may be non-efficient for the collection purpose.

In other words, virtual impactor or mechanical cyclones may be well-known and familiar particles concentrators. However, in spite of the existence of very efficient and collecting and focusing impactors, which are very efficient even with nano-particles size that are also small in size, such as the sonic impactor, they still run the risk of viruses or bacterial deposition of its surface and complicate the option of combing then with the elimination step.

Furthermore, the use of impactor of mechanical cyclone does not form a new technology, less complicated in structure or cheap products; therefore, they are not chosen as an option.

(25)

~i Conceptual Product Design CH3812 p~

TU

Delft ______

F_in_al_R_ep_o_rt_C_PD_-_3_3_33 _ _ _ _ _ _ _ _

s

EtJ

Electrostatic Forces may be used to affect the targeted bioaerosols and manipulate their flow path, to capture them with or without harming them. Therefore, they have an additional research benefit, which is the ability to collect the bioaerosols without causing them definite harm. This property may be an advantage to research the collected bioaerosols and identify them, which may indicate the protection procedures required against the threat of such contaminants, mainly in case of the spread of airborne disease.

When comparing the ability of mechanical forces applied by cyclones or impactors with electric forces to capture the particles without damaging them, the electrostatic forces have the highest priority and ability. Therefore, since the required product is designed for hospita Is as early adapters for such product, it is important to realize that the hygiene level there should always be high and large number of contaminants and their impact are in continuous research, therefore, from this point, the designed product uses the knowledge from electrostatic precipitators to design a new product that is capable of capturing and concentrating the bioaerosols as who Ie, while increasing the ESP

efficiency for such particles si ze and concentration to adapt it to the requirement and conditions of the design.

(26)

1J!:i..

.

T

U

Delft ______

F_in_a_1 R_e_p_ort_C_P_D_-_3_33_3 _ _ _ _ _ _ _ _

s

èl)

Table 2.2: Comparison between Cyclone, Impactors and Electrostatic

CYCLONES

VIRTUAL IMPACTOR

ELECTROSTATIC PRECIPITATORS (ESPs)

[31]

• Low capital cost

(relatively cheap to buy and instalI) • Ability to operate at high temperatures • Low maintenance requirements (because of no moving parts)

• High efficiency with collection of big

particles> 1 micron and much smaller.

• Ability to operate at high temperatures. • Low capital cost

(relatively cheap to buy and instalI)

• Low maintenance. • Efficient for high

particIe concentration.

• Low operating cost (except at very high efficiencies)

• Very high efficiency, even for smaller particles (Industrial systems high efficiency of 95% in capturing particles in the range of

0.01-10

microns.) • Ability to handle very

large gas flow rates with low pressure losses

• Abi to remove as

• Relatively low efficiency (especially for the smaller particles) • Limited to dry particles

(not operating weil on mist)

• High operating cost (expensive to run, because of pressure • Low efficiency with

particles of

1

microns. • Particles may bounce

from the collection surface upon impaction. • Collected particles may

re-entrain.

• Walilosses between the impactor stages may be considerable.

• Very large partieles may break-up upon

impaction, especially at high impaction

veloeities.

• High pressure loss. • High ca pita I cost

(expensive to purchase and instalI).

• Taking a lot of space. • Not flexible once

installed.

• Failure to operate on particles with high electrical resistivity. • Does not control

gaseous emissions. • Not very flexible, once

(27)

Final Report CPD - 3333

_ _ _ _ _ _ _ _ _ _ _ _

"

SE

""

"

weil as wet particles

•

Mostly generates Ozone.

(mist ok) Requires frequent filtration.

•

Temperature flexibility

2.3.2.

Elimination Evaluation

A number of the possible options for elimination have been evaluated earlier, they were found to be non-suitable and therefore not considered anymore. However, part of them, chemica I disinfection and ozone treatments, have been evaluated further for the sake of comparison with the potentially chosen method for elimination, UV light.

The following table represents a qualitative comparison for efficiency between the possible elimination processes summarised from variety of sourees.

rison between Possible Elimination Processes

UV Radiation - • Kills bacteria and viruses by Damaging their DNA/RNA. Ultraviolet • Very effective in

germicidal laboratories.

irradiation (UVGI) • UV disinfection is effective at inactivating most viruses, spores, and cysts.

Chemical Disinfection

• A physical non-chemical process.

• No residual effect that can be harmful to humans. • Short contact time required. • Requires "Iess" spaces.

Used by vaporizing or spray

Ozone Generator • Strong oxidizer that kills microorganisms effectively. • Aerial disinfection, it is gas

and can penetrate eveiywhere.

• No harmful residues: ozone is converted back to stabie oxygen and ozone conc. drops to 0.02 ppm.

• Effective for purification of unoecu

• can disinfect air close to the lamp due to limited

penetration capacity. • Efficiency reduces with

increasing humidity of air. • Inefficient mixing can allow

microorganisms to get through the UV rector with insufficient treatment. • Dosage depends on: area,

resident time, and intensity. • UV-Organisms destruction

may be reverse by the "repair mechanism," known as photo reactivation, or in the absence of light known as "dark re ir."

Usually difficult to decompose, leaving toxic chemical residues that are hazardous to human health.

• Ozone's toxicity at concentration

>

1 ppm. • High concentration required

for disinfection (at 2.5 ppm, 90% efficiency).

• The minimum ranges of ozone disinfection are set as

adequate ranges for air purification (0.5- 2.5 ppm). • Has limited studies, therefore,

(28)

Jr;:;

'

T

U Delft ______

F_in_al_R_ep_o_rt_C_PD_-3_3_33 _ _ _ _ _ _ _ _

s

ëtJ

I·

Low energy consumption. it in air purification.

Based on literature and on the results presented in the table above, the UV disinfection has proven to have high efficiency when sufficient intensity and time of exposure are supplied. It has no adheres effects when designed weil in ducts or enclosed systems. Hence it is effective and safe to use.

2.4. CONCLUSIONS

Based on all data pres ~ted for options, their evaluation and relevant appendixes, the two chosen function doe e designed product are: collection and elimination. For the collection process, be valuated option was the use of electrostatic forces to capture the desired bioaerosols; therefore, this option was chosen for the design. On the other hand, for the process of elimination, UV light seems to be best option; therefore, the use of UV irradiation is chosen. However, although the low-pressure types of UV lamps (presented earlier as UV-C or UVGI) are normally used, the right choice of required UV lamp, intensity and characteristics are discussed in the detailed design chapter based on efficiency and economie considerations.

Hence, the chosen product consumes electricity for two steps:

To charge particles and capture on a surface to prevent them from flowing out with the air stream or to convert the electric energy into "mechanicai" by manipulating the airflow pattern causing centrifugal pattern that separates the particles by the centrifugal forces created by the electric wind generated from the discharge electrodes.

On the other hand, the electricity is converted into light and radiation generated in the UV lamp, which terminates the targeted bioaerosols.

Such design has no mechanical parts, which indicates that it may not require costly maintenance. Furthermore, it is multiple functional. That means that it can be used for air disinfections in normal status when both functions are considered. On the other hand, it is also possible used for concentration and collection of bioaerosols without damaging them for purpose of research or immunity preparations.

2.5. Economie and market considerations

This sub chapter expresses a general overview for the air purifiers' market. The overview considers air purifier for domestic or industrial use in general because the air purification system is in continuous developments phase, hence domestic air purifiers may be further developed and updated for other conditions.

According to the EPA (U.S. Environment Protection Agency) the air in even the largest and most industrialized cities is less toxic than the air around in typical homes. It is estimated the most people spend 90% or more of their life indoors. Therefore, the

(29)

_ _ _ _ _ _ _ F_in_a_1 R_e_p_o_rt_C_P_D_-_3_3_33 _ _ _ _ _ _ _ _ _ _

S

Ët)

quality of the indoor air we breathe everyday become critica I and the awareness for this danger becomes more published and weil known [76].

The world market for air filtration and purification through the year 2003 reached the value of $6 billion. Sales of filters to purifying air in homes, commercial buildings, and industrial plants around-the-world will rise from $ 6 billion in the year 2003 to more than $ 6.3 billion in 2007 based on the new forecast appears in the continually updated on line report Air Filtration and Purification: World Markets published by the Mcilvaine Company of Northfield 11, where the largest contribution to this apart is from air purification in hospita Is, pharmaceutical and medical device companies due to the important and restricted health considerations. The market in pharmaceuticalj

biotechnology sector is expected to keep growing all over the world; and based on that, U.S.A. Japan and Germany may be considered to be the leader users for highly efficient air purifiers and followed by France, china, United Kingdom, Italy, South Korea, Spain and Indonesia and others; which indicate the possibility to broaden the market worldwide [74],

Each year in the U.S., an estimated 17 million to 50 million people are infected with the influenza virus. Influenza also results in approximately $3 billion to $15 billion annually in direct and indirect costs, including an estimated 70 million missed workdays and approximately 38 million missed school days [75]. Because the influenza virus is

airborne, it is easily transmitted, placing nearly everyone at risk of exposure. This is why areas where people gather, such as schools, homes, and offices, are likely locations for catching the f1u. The most effective way to prevent influenza is by air purifier.

The residential market represents more than 10% of the total, while the biggest

residential market in the world is U.S. where forced air heating is common. Domestic air purifiers, which comply with the American Lung Association standard [4], cost almost $3,000- $6,000. And since the new home construction increase (at least based on the data obtained from the U.5.A) with time, the residential air purifiers market grows respectively.

The commercialjinstitutional market is twice the size of the residential market and is more evenly distributed worldwide. Sales in this sector will surpass $ 3 billion by 2008.

The Electronics industry is a big user or air purification equipment.

It

is rebounding in all areas of the world, especially the microchips and semi conductors industry. Asia for example is known as one the growing and developing area; therefore, it will experience the largest growth in this segment [74].