pollutant migration from manufacturing shop- floor … · the kanomax, climomaster, model 6521, low...

International Journal on Architectural Science, Volume 4, Number 3, p.98-113, 2003

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POLLUTANT MIGRATION FROM MANUFACTURING SHOP- FLOOR TO OFFICES WITHIN THE INDUSTRIAL BUILDING – A CASE STUDY IN SINGAPORE N.H. Wong and T.P. Ngiam Department of Building, School of Design and Environment, National University of Singapore, Singapore (Received 27 November 2002; Accepted 25 April 2003) ABSTRACT This paper discusses the key findings of an indoor air quality (IAQ) audit to assess the IAQ status of the offices within a printing factory. Various objective and subjective measurements to co-relate the employees’ perception of the physiological and physical parameters were carried out. The objective measurements covered the chemical, physical and biological contaminants, and tracer gas tests for possible cross-contamination. The closest available local ENV 1996 guidelines were used to benchmark the performance standards. The study shows that high concentration levels of Total Volatile Organic Compounds (TVOCs) and formaldehyde (HCHO) were observed at all sampling locations, with indoor to outdoor ratio of greater than 2. This indicates a strong indoor generating source of TVOCs and HCHO. It is not surprising since the building uses substantial quantities of solvents in their daily operations coupled with an ineffective ACMV system and layout of the production spaces. 1. INTRODUCTION Many indoor air quality research studies have been focusing on commercial office buildings in Singapore. Since the release of the ENV IAQ guidelines [1], many expanded and extended IAQ research studies had been carried out by relevant researchers and students in the commercial buildings which further enhances the public awareness of the occupants and owners of the commercial buildings [2-8]. However, very limited studies have been conducted to monitor the IAQ status of offices within the industrial building [9-11]. There are also no guidelines for the design of offices within the industrial building. With improper zoning of the air conditioning systems, coupled with the poor compartmentalization of the offices from the production areas, cross contamination of the pollutants generated from the production areas could occur. This paper therefore discusses a study on the IAQ monitoring and assessment of offices in the production floor of a printing factory in Singapore. The key objectives of this study are: To monitor the level of Indoor Air Quality of

a printing factory.

To evaluate the level (if any) of cross contamination from the production floor to the offices located within the production floor.

To tabulate and compare the indoor air quality results with the relevant guidelines or industrial standards.

To correlate the occupants’ subjective measurement with the objective IAQ results so as to validate the occupants’ response towards their indoor work environment.

To propose the engineering solutions and improvement to enhance the quality of the indoor air environment.

2. METHODOLOGY 2.1 Introduction

Mainly, the IAQ objective measurements and subjective evaluation cover the production offices on the production floor located at the first storey of the printing factory. For comparison and cross-referencing between the IAQ profiles of the production offices and production floor, a few sampling points were also taken in the production floor closest to the production offices. These sampling points from the production floor will help to evaluate the level of any air filtration and ex-filtration between these two zones. With this data, it will be able to provide a broad overview whether the personnel working in the production offices are also likely to be exposed to the pollutants from the production floor. Fig. 1 shows the methodology adopted for this study.

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Fig. 1: Methodology adopted for this study 2.2 Objective Measurements 2.2.1 Instrumentation and Methods

The measurement protocol was taken from the guidelines set in the Ministry of Environment for good indoor air quality in office premises [1]. The

printing factory chosen for the study consist of the production floor, offices and other supportive departments. As mentioned earlier, one of the objectives is to examine the possible cross-contamination between the production floor and the production offices. As such, a total of eight indoor sampling points, which cover the production floor


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and production offices, and an ambient point were used for the 7 days continuous real-time monitoring of the chemical concentration. This is to allow for comparison of chemical concentrations between the indoor and outdoor air, and possible cross-contamination within the production zone. The 7 days covered the weekends as well as weekdays so as to be able to audit the overall IAQ profile for the total operations of the factory. 2.2.2 Chemical Measurement

The continuous real-time monitoring of the chemical pollutants, such as carbon dioxide (CO2), carbon monoxide (CO), formaldehyde (HCHO) and total volatile organic compounds (TVOCs) were carried out with the use of : Bruel & Kjaer (B & K) multi-gas monitor,

type 1302.

Bruel & Kjaer (B & K) multi-point sampler and doser, type 1303.

Bruel & Kjaer (B & K) application software, type 7620.

The overview set-up of the multi-gas monitor in the General Manager’s office is shown in Figs. 2 and 3. 2.2.3 Spot Measurement

Spot Measurement was adopted to measure the concentration level of ozone (O3). Dasibi, model 1008-PC ozone meter was used to measure the ozone level. The locations of the eight sampling points were near to the vicinity of the sampling points used for the continuous real-time monitoring. 2.2.4 Biological Measurement

A single-stage Andersen N6 sampler was used to collect the biological samples. Two sets of samples were collected for each sample point, one at 1.2 m above ground and another just below the air diffuser. 2.2.5 Particulate Measurement

Dust-Trak aerosol monitor, model 8520 was used for the spot measurement of the concentration of the suspended particulate. It provides a continuous gravi-metric measurement of pollutants and measurements of the size or aerosol diameter are stored in the monitor as mass concentration, in units of µgm-3. 2.2.6 Thermal Comfort Measurement

The Kanomax, climomaster, model 6521, low velocity handheld instrument was used to measure

the dry bulb temperature, relative humidity and air velocity. This instrument is a three in one user friendly portable instrument, which uses a super-sensitive sensing probe, capable of measuring the three basic thermal comfort parameters. 2.3 Subjective Evaluation The printing factory was given 60 questionnaire forms specially targeted at personnel in the production offices and production floor nearest to the office. During the walk-through and questionnaire survey, interviews were also conducted with the appropriate personnel to obtain general information of the plant operations. By comparing the objective and subjective monitoring results, it provides an overview of the IAQ performance level in the total production office, partial production floor and overall perception of the entire factory. The medium used for the subjective measurement is through a self-administrated simplified questionnaire survey form [12], to evaluate the occupants’ perception of the physical environment and physiological response. To provide a more accurate perception response, the author and appropriate manager helped to translate and explain the questionnaire, as they are filling up the forms. The questionnaires were circulated to all employees occupying the researched area through the production managers of the factory.

Fig. 2: Multi-gas monitoring system


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Fig. 3: Laying of sampling tubes below the false ceiling

2.4 Data Guidelines for Objective Mea-

surement The only guideline available for the indoor air contaminants threshold concentration is from the good indoor air quality in office premises by the Ministry of Environment in October 1996 [1]. This guideline is mainly used for the air-conditioning office premises in commercial buildings in Singapore. The printing factory falls within the regime of the Ministry of Manpower, in which the safety, health, welfare and related environment matters affecting the persons working in the factories are legislated by the Factories Act (Chapter 104). In this legislation Act, there is no IAQ standard or cross-reference to other governmental arm for the factories. Table 1 presents the recommended maximum concentrations for specific indoor and classes of air contaminants, as well as the specific physical parameters set by ENV 1996. 2.5 Data Guideline for Subjective Mea-

surement The data tabulated from the questionnaires were used to evaluate the perception of the IAQ performance level, with reference to the physical and physiological parameters. The initial elaborated questionnaire was formulated in the “European audit project to optimise indoor air quality and energy conservation in office building”[13]. However, to adapt to the local environment, the simplified IAQ questionnaire [12] was used.

3. CASE STUDY 3.1 Description of the Building The building is a three storey industrial building situated in an industrial zone. It has a rectangular floor plan dimension of 48 m by 60 m with an area space of 2,880 m2. This twenty-year-old building was constructed and had been occupied since 1982. The main production activity is located on its first storey. The second and third storeys are mainly occupied by the administration offices. The main printing production is located at the central part of the first storey with high ceiling, with the supportive production and logistic offices surrounding the perimeter of the production floor. The production floor occupies an approximate dimension of 36 m by 48 m, which is equivalent to 1,728 m2. Fig. 4 shows the typical floor plan of the first storey. The main manufacturing workforce works on a 24 hours round-the-clock operation, with a 12 hours rotational shift. The total workforce is about 160 with the following break-down: 100 employees from the manufacturing 60 employees from the office on a normal

shift working from 8 am to 5 pm. The continuous chemical monitoring was conducted from 1st February (Friday) 2002 to 8th February (Friday) 2002. The printing equipment include the printer rollers, copying machines, laser printers, ovens, paper cutters and printing plate machines to support the


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printing and laminating processes. In the process, many chemicals are used i.e. solvent paint based chemicals, printing inks, lubricating oil, film developing and processing chemicals. Some of the major sources of chemical pollutants include; aromatic aliphatic hydrocarbon solvent, ketone

blend solvent, acrylate ester of trimethylol propane, isopropanol, butyl acetato, propyl alcohol, ethylene glycol, oleoresinous varnish, naphthenic acids, disodium dodecyl (sulphophenoxy) benzene-sulphanate, disodium citrate, potassium silicate, glycerine, hydroquinone, etc.

Table 1: Recommended threshold values of various indoor contaminants and physical parameters set by ENV 1996

Parameter Limit for Acceptable Indoor Air Quality Unit Recommended maximum concentrations of specific indoor air contaminants Carbon dioxide (8 hours average) 1800

1000 mgm-3 ppm

Carbon monoxide (8 hours average) 10 9

mgm-3 ppm

Formaldehyde (8 hours average) 120 0.1

µgm-3 ppm

Ozone (8 hours average) 100 0.05

µgm-3 ppm

Recommended maximum concentrations of specific classes of contaminants Suspended particulate matter 150 µgm-3 Volatile Organic Compounds 3 ppm Total Bacteria Counts 500 CFUm-3 Total Fungal Counts 500 CFUm-3 Guideline values for specific physical parameters Air temperature 22.5 – 25.5 oC Relative Humidity ≤ 70 % Air Movement ≤ 0.25 ms-1

Fig. 4: Typical floor plan of the first storey


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3.2 Plant Walk-through Inspection and Air-Conditioning and Mechanical Ventilation (ACMV) System Familiarization

The inspection revealed that during the production, the printing process uses copying machines, laser printers, solvents, cleaning chemical agents, additives, paint based chemicals, printing inks, lubricating oil, film developing & processing chemicals, etc. In short, many strong volatile organic chemicals are used continuously during the daily production processes. The ACMV uses the constant air volume (CAV) system, which are supplied by multiple air handling units to different zones at different storey. Conceptually, multiple air handling units (AHUs) are serving the designated zones for different offices and operations. Therefore, there should be no cross-mixing of the air-conditioning air between the zones. The studied zone is at the first storey, which has a designated air handling unit serving the production, pre-press and designing offices. Also there are four other air handling units, which

are mainly designed to serve the entire production floor as an independent zone. These AHUs supporting the production floor run continuously on a 24 hours operation. At the first storey, another air handling unit is solely serving the human resource and conference rooms, which operates only during the office hours from 8 am to 5 pm, on Mondays to Fridays. Fig. 5 shows the single-line diagram of the supply air duct based on the site judgment. The supply air is supplied through the duct above the ceiling via the diffuser. The return air to the AHU room is through the duct positioned at strategic locations and rooms. The AHU room at the first storey serving production, pre-press and designing office, seems to appear very cramped and may impair the efficiency of the mixing air process in the AHU room. Another peculiar observation made in this AHU is the tiny ducted fresh air intake (without fresh air fan) to serve an area of about 480 m2 with many different chemicals used in the pre-press and designing offices. The fresh air volume is likely to affect the efficiency of the dilution in this production office. The indoor and outdoor sampling points are shown in Fig. 4.

Fig. 5: The supply air ducts for the production office


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4. DATA ANALYSIS 4.1 Objective Measurement and Data

Analysis The continuous real-time monitoring was carried out at the nine sampling points where chemical parameters, consisting of CO2, CO, TVOCs and HCHO were measured. The spot measurement was conducted for the chemical parameter of O3. All the mean values recorded were based on averaging time of eight hours of exposure. 4.1.1 Carbon Dioxide (CO2)

The ENV 1996 recommends a threshold level of not exceeding 1000 ppm for an average period of eight hours. It can be seen in Fig. 6 that the values of carbon dioxide concentration levels in the nine sampling points range between 310 ppm to 938 ppm with a mean value of 653 ppm. The CO2 level profile reflects a higher CO2 level during the daytime as compares to the night at all internal locations. This regular pattern of higher CO2 level corresponds directly with the higher human loading during the office hours and gradually reduces during the evening due to the lower workforce only

from the production department. As a whole, the concentration levels are well within the recommended limits. 4.1.2 Carbon Monoxide (CO)

The recommended threshold limit specifies in the ENV 1996 is less than 9 ppm for an average eight hours period of exposure. Fig. 7 reflects the CO concentration profile and the values range between 0 ppm to an estimated 14 ppm with an average mean value of 6 ppm. The outdoor CO profile at the fresh air inlet has a regular pattern of showing distinct peaks during the morning hours with a maximum level of 14 ppm and tapers off in the later part of the day. The strong likelihood cause could be contributed by the car park just beside the fresh air inlet and near to the main road. The other clear indicator which reflects a strong outdoor source is seen by the indoor to outdoor ratio of being less than one. Although the 8 hour mean value of 6 ppm is within the threshold limit of 9 ppm, the regular instantaneous surge of 14 ppm during the peak morning hours exceeds 9 ppm. It may be a concern which should be addressed to bring down to the acceptable level.

Carbon dioxide Concentration ProfileENV Threshold value = 1000ppm

0100200300400500600700800900

1000

Location

Con

cent

ratio

n (p

pm)

Minimum 370 375 381 381 376 370 370 371 349Maximum 770 690 700 706 938 589 551 664 595Mean 653 611 645 621 629 524 515 572 391

1 2 3 4 5 6 7 8 9

Fig. 6: Carbon dioxide concentration profile


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Carbon Monoxide Concentration ProfileENV Threshold value = 9ppm

0

2

4

6

8

10

12

14

Location

Con

cent

ratio

n (p

pm)

Minimum 1.34 1.23 1.4 1.38 1.32 3.99 4.72 1.88 14Maximum 0.04 0.07 0.13 0.18 0.09 0.03 0.01 0.22 0.41Mean 0.80 0.80 0.83 0.79 0.77 1.32 1.41 0.81 5.91

1 2 3 4 5 6 7 8 9

Fig. 7: Carbon monoxide concentration profile

4.1.3 Total Volatile Organic (TVOCs)

The local ENV Guidelines for the threshold level of TVOCs (reference to Toluene) is 3 ppm. The continuous profile of TVOCs concentration levels are illustrated in Fig. 8. The values range at a low value of 5 ppm to a high value of 53 ppm with an 8 hours mean value of 40 ppm. Even the lowest value goes beyond the acceptable threshold limit of 3 ppm. The TVOCs level is very high and certainly it is of concern both for the indoor working environment and health impact for the employees. It is noted that the production floor registers a high mean value of 40 ppm and the production offices register an average value of 17 ppm, which clearly shows a high cross-contamination from the production floor to the office areas. Despite the designated air-conditioning zoning served by the independent air handling unit, cross infiltration still takes place, owing to the possibility of the shortfall of the differential atmospheric pressure between the two zones. To doubly confirm the high cross-contamination from the production floor to the offices, tracer gas using sulphur hexafluoride was dosed into the production environment for about 5 minutes. The results show very clear evidence of cross contamination of SF6

gas from the production floor to all offices zones. Smoke pen test was also used to trace the air flow between the production floor and the offices (see Fig. 9). Another significant observation was the concentration level of 6 ppm detected at the fresh air inlet grille, which exceeded the allowable limit by 2.1 times. Naturally, it is a concerning level for a polluted ambient air intake, which the air is supposedly to be fresh. The other crucial point to note was the high indoor to outdoor TVOC ratio of 2.4 to 6.3, which indicates a high internal source of TVOCs that was recycled into the return air or short-circuiting into the fresh air inlet. Ineffective dilution process and poor exhaust ventilation may have contributed to the high TVOCs concentration levels. There is a high possibility of ex-filtration of TVOCs from indoor to outdoor, through window seals, cracks from the wall and other openings, and subsequently channeled back into the fresh air inlet. This could be also due to the accumulating and stacking effects of the continuous airborne exposure of the high usage of volatile organic compound in the 24 hours operations of the printing process for the past 20 years.


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TVOCs Concentration Profile

ENV Threshold value = 3ppm

0

10

20

30

40

50

60

Location

Con

cent

ratio

n (p

pm)

Minimum 10.1 9.3 8.4 9.4 8.1 15.8 17.6 10.2 4.6Maximum 45.5 44.1 46.5 55.3 51.9 48.5 53.2 41.7 15.1Mean 16.6 15.9 18.6 16.5 15.7 35.9 39.9 15.3 6.4

1 2 3 4 5 6 7 8 9

Fig. 8: TVOCs concentration profile

Fig. 9: Use of smoke pen to detect cross contamination


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4.1.4 Formaldehyde (HCHO)

The local ENV 1996 guidelines specify an exposure level not exceeding 0.1 ppm for the 8 hours exposure. The concentration profile of formaldehyde for the 9 locations exceeded the recommended level which can be shown in Fig. 10. The overall profile reflects a very high concentration of HCHO ranging between 0.3 ppm to 3.9 ppm with 8 hours mean value of 3 ppm. By comparing the acceptable level of 0.1 ppm, these significant high levels obviously present some concerns and potential negative health effects to the employees. The indoor to outdoor ratio ranges from 2 to 5.5, which indicates a high content of indoor generating sources. On top of that, even L9 (the point near to fresh air inlet) was at a high value of 1.6 ppm, which poses a concern that the HCHO may be re-circulating via the fresh air inlet. Again, this would be a strong indicator of short-circuiting effect. The result shows that unless drastic steps are taken to minimize the HCHO level, the HCHO level may continue to escalate to a life threatening point. 4.1.5 Ozone (O3)

The recommended level specified by the ENV 1996 guidelines for 8 hours period of exposure should not exceed 0.05 ppm. Owing to the non-

availability of continuous real-time monitoring of ozone, spot measurement was adopted with a portable ozone meter to assess the level of ozone concentrations at the 9 sampling locations. This chemical parameter was also monitored to assess the ozone level, which may be possibly emitted by the paper and film laser printer, film developing machines and photocopying machines used in the pre-press and designing offices within the production offices. Table 2 confirms the concentration levels at all indoor locations are generally within the acceptable level, though the above machines are used. 4.1.6 Biological Pollutants

For total bacteria and fungi growth, the recommended maximum thresholds are 500 cfum-3 for an acceptable indoor air environment. Table 2 shows the bacteria and fungal counts at the occupant and air supply levels. All locations were within the acceptable level, except at the occupant and air supply levels for location # 1, where the bacteria counts were at 519 cfum-3 and 678 cfum-3 respectively. This could be contributed by human activities. Thus, all locations are within the recommended counts of 500 cfum-3, though one location exceeds slightly.

Formaldehyde Concentration ProfileENV Threshold value = 0.1ppm

00.5

11.5

22.5

33.5

44.5

Location

Con

cent

ratio

n (p

pm)

Minimum 0.61 0.54 0.53 0.59 0.44 1.17 1.25 0.65 0.29Maximum 3.05 3.00 3.13 3.74 3.50 3.71 3.87 2.87 1.58Mean 1.13 1.05 1.31 1.10 1.06 2.68 2.96 1.00 0.53

1 2 3 4 5 6 7 8 9

Fig. 10: Formaldehyde concentration profile


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Table 2: Location of sampling points, ozone and particulate concentration, microbial counts and thermal comfort condition ENV Threshold limits

0.05 ppm 150 µgm-3 500 cfum-3 500 cfum-3 22.5oC to

25.5 oC ≤70% cfum-3

Viable bacteria count Viable fungal count Locations

Ozone (ppm)

Particulate count (ppm)

Air supply

(cfum-3)

Occupant level

(cfum-3)

Air supply

(cfum-3)

Occupant level

(cfum-3)

Air dry bulb temp. (oC)

Relative humidity (%RH)

Mean air

velocity (ms-1)

L1 Manager Office 0.006 24 876 519 35 26 23.5 67.8 0.23

L2 Visitor Room 0.002 28 44 53 282 9 23.5 61.5 0.15

L3 Production Office

0.008 26 150 229 53 26 22.1 71.9 0.08

L4 Pre-Press Room 0.008 19 18 62 53 114 22.6 63.4 0.14

L5 Designing Room 0.005 21 44 62 35 26 22.6 66.4 0.07

L6 Production Floor

0.022 152 62 9 150 88 23.9 55.7 0.1

L7 Production Floor

0.035 137 273 176 194 88 23.0 54.4 0.09

L8 Inside AHU Room 0.060 23 79 9 23.6 66.9 1.75

4.1.7 Particulate Pollutants

In the ENV guidelines, only the particulate with aerodynamic diameter of 10 micron and less, are of concern in the readings. The recommended threshold for the short term exposure (over 8 hours period) in the office premises is 150 µgm-3. Table 2 shows the particulate concentration, which ranges from 19 to 152 µgm-3. The concentration of 152 µgm-3 is at location # 6, which is located on the production floor. This concentration could be contributed to the paper dust particles generated by the paper shredding process at the end process of the printing equipment. Despite the off limit of one location, the other locations do not pose an airborne particulate contamination concern in the offices. 4.1.8 Thermal Comfort Measurements

The indoor dry-bulb temperature ranged from 22.5oC to 25.5oC, relative humidity was below 70% and maximum air movement was below 0.25 ms-1 at workstation levels. The thermal comfort readings are shown in Table 2. From the measurements, the readings for the temperature, relative humidity and mean air velocity at all locations seem to be well-controlled within the thermal comfort zones.

4.2 Subjective Measurement and Data Analysis

A total of 60 questionnaire forms were given to the appropriate employees involved in the IAQ monitoring project. Out of 60 forms distributed to the respective heads of department, 54 forms were returned and used for the data analysis in the subjective measurement. The 54 respondents consists of 63% males and 37% females with 67% of age above 30 years old and 33% of age between 20 to 30 years old. 4.2.1 Questionnaire Assessment & Discussion

The symptoms of sick building syndrome (SBS) for both the production floor and offices are shown in Fig. 11. It can be seen that the production printing floor and production offices share the 4 similar symptoms, such as the rash / irritated skin, dry skin, flu-like symptoms and headache. The high percentage of the above complaints seems to lead to some strong indications of problems relating to air quality. The overall complains of the workers on the physical parameters of the production floor and offices are shown in Fig. 12. The working comfort is not in the top five listing indicates a less concern or priority for them. However, production printing floor seems to focus their attention on the


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air quality concern of 47% and 43% of smelly air and dusty air respectively. Similarly, the production offices also rank the top 2 placing on stuffy and smelly air of 42% and 33% respectively. Fig. 13 further reinforces the major sources to smelly perception of poor air quality. The respondents’ complaints reflect a high percentage of concern due to paints, solvents,

chemicals and solvent-based cleaning agents contributing to the poor air quality. From both results of the production floor and offices, it seems that the air quality is a concern which needs to be further analyzed and co-related with the objective measurement to surface some solid evidence for status of the air quality.

0%

10%

20%

30%

40%

50%

60%

70%

Rash /

irritated skin

Dry skin

Dry eyes

Wateringeyes

Runny nose

Blocked /

Stuffy nose

Flu-likesym

ptoms

Headaches

Lethargy

Other

symptom

s

Symptoms of SBS exhibited by the workers

ProductionOffice

Fig. 11: Symptoms of SBS exhibited by the workers in both production floor and offices

0%

5%

10%

15%

20%

25%

30%

35%

40%

45%

50%

Cold

Hot

Dry

Still

Stuffy

Sm

elly

Dusty

Lighting

Working

Com

fort

Cleanliness

Overall complaints of the workers on the physical parameters

Production

Office

Fig. 12: Complaints of the workers on the physical parameters of the building


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0%

5%

10%

15%

20%

25%

30%

35%

40%

Food Paint (ink &paint)

Photocopier Stationery Pungent(Chemical &

Cleaning agents)

Sources Contributing To Perception of " smelly " Air.

ProductionOffice

Fig. 13: Sources of smelly air 4.3 Co-relation between Objective and

Subjective Measurements The subjective survey analysis reflected a significant high percentage of skin problems and irritation, headaches, eye irritation and flu-like symptoms for employees working in the production floor as well as offices. This high percentage of complaints seem to correlate well with the high concentration level of TVOCs of high mean value of 40 ppm and formaldehyde of high mean value of 3 ppm. Studies have shown that TVOCs are known to be associated with sore throat, eye irritation, headaches, nausea, drowsiness and fatigue to high exposure of TVOCs. In addition, acute exposure to formaldehyde may cause eye, nose, ear and throat irritation which lead to skin rash, coughing and wheezing, fatigue and severe allergic reactions. At this juncture, the evidence seems very clear and supportive that the physiological symptoms correlate well and represent the poor air quality in the indoor work environment. The data analysis revealed that the respondents are generally satisfied with the overall thermal comfort, which corresponds to acceptable thermal comfort limits in the objective measurement. Hence, the objective and subjective measurements tally well with the co-relationship. Despite the high percentage of 43% and 17% recorded for the production floor and offices

respectively in the subjective measurement, particulate concentrations show that only location # 6 (production floor) is off-limit by 152 µgm-3. This does not pose a concern. There is a likely chance that the some respondents may be influenced by the ‘odour‘ in the air which they may perceive as dusty air/unhealthy. 5. CONCLUSIONS Judging from the evidence in the continuous real-time monitoring and subjective perception of the occupants’ response, there are many unfavorable results and symptoms, which indicate the poor indoor air quality of the factory. The concentration levels of TVOCs and HCHO in the production floor and offices show clear evidence of cross-contamination between these two areas in the factory. Tracer gas technique and smoke tests were used to further confirmed the cross contamination. However, the CO2, CO and O3 are within the threshold limits. The biological levels of bacterial and fungal at all indoor locations were also within the recommended threshold limit of 500 cfum-3. The particulate counts were far within the threshold limit of 150 µgm-3 at all locations. The thermal comfort parameters were also within the comfort zone. By applying the compiled data from the subjective measurement, it revealed many unfavorable health symptoms. The health symptoms are closely associated with exposure to high concentration of volatile organic compounds.


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From the above data comparison, it reflects a very close relationship with the objective and subjective measurements. 6. RECOMMENDATIONS 6.1 Buffer Zone Acts as Pressure

Equalization Chamber The study shows that the probable cause of cross contamination is due to the lack of provision of buffer zone between the production floor and offices. The pressure differential in the production office is also found to be lower than the production floor. Thus, there is a sudden gush of polluted air from the production floor when these office doors are open. It is strongly recommended that an enclosed buffer room be constructed just directly opposite the existing swing glass door to create a pressure equalization chamber as shown in Fig. 14.

To integrate the overall approach, the ACMV has to be retrofitted such that the pressure differential cascades at higher pressure from production office to pressure equalization chamber via the production floor. The proposed pressure differential (mm of H2O) at Production office is 3 mm, pressure equalization chamber is 2.5 mm and production floor is 1.5 mm relative to outside conditions [14]. With this cascaded pressure differential profile, there is little chance for the direct infiltration from the production floor to the offices. To achieve the cascaded pressure differential relative to outside condition, the building pressurization has to be re-designed and re-configured through proper control of the exhaust, make-up fresh air intake and air distribution. Furthermore, each zone is to be installed with a permanent barometer to indicate the pressure differential so as to allow the maintenance crews to monitor and audit the readings during their routine check.

Fig. 14: Provision of pressure equalized buffer zone to minimize cross contamination


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6.2 Source Elimination, Minimization and Substitution

Source control is an effective means of minimizing, eliminating and containing the indoor air related problem, due to the fact that this is the main root cause of the indoor pollutant emission. But, this may not always seem feasible owing to the operational needs, requirements and constraints. The factory has been using a large amount of the chemicals in manufacturing their products and it seems that these are the basic chemicals needed for the process. Despite the basic requirements, it is recommended that there may be a new paradigm shift by using alternative environment-friendly solution and operations to produce the similar end products. It is proposed that an IAQ spin-off task force comprising of managers, engineers, quality assurance, human resource personnel and purchasers, to champion this committee, with its mission or goal for a healthy working indoor environment. The main issues for these committees are to address the unfavorable sources contributing to the poor IAQ, which include sources elimination, minimization and substitution. 6.3 Ventilation System Thorough evaluation and observation of the current production operations and equipment using chemicals during the process, seem to operate with ineffective localized exhaust system and majority of the chemical related processes are without any exhaust system. These airborne chemical pollutants are simply emitted into the work environment, mixed with the air-conditioning air and return back to the air-handling unit. In fact, these pollutants can be removed by installing effective mechanical exhaust system coupled with appropriate localized hoods. The high CO concentration at the fresh air inlet could be due the fresh air inlet grill being located at very close proximity to the car park. Thus, it must be relocated to a relatively safe distance. In addition, to counter-balance of the proposed dilution and exhaust ventilation system, the fresh air inlet capacity has to be redesigned. To monitor and alarm the abnormal pre-set CO concentration level at the fresh air inlet, CO sensor should be installed with audio and video devices at the strategic control station. This CO sensor can be linked to the appropriate demand controlled ventilation, to modulate the fresh air inlet accordingly to meet the safe acceptable level.

REFERENCES 1. ENV, Guidelines for good indoor air quality in

office premises, Ministry of the Environment, Singapore (1996).

2. Akbar Mydin, “An indoor air quality audit of a commercial building”, Unpublished Master of Science dissertation, School of Building and Real Estate, National University of Singapore (1999).

3. Ee Chee Koon, “IAQ in commercial buildings in Singapore”, Unpublished Master of Science dissertation, School of Building and Real Estate, National University of Singapore (1997).

4. Lee Lit Phong, “Detailed indoor air quality study of two zones in an air-conditioned office building”, Unpublished Bachelor of Science dissertation, School of Building and Real Estate, National University of Singapore (1997).

5. Lim Ann Hwee, “Indoor air quality and energy implications in the use of VRV system for office building”, Unpublished Master of Science dissertation, School of Building and Real Estate, National University of Singapore (2001).

6. S.C. Sekhar, K.W. Tham, D. Cheong, S.C. Foo and M. Susithra, “Intergrated IAQ and energy audits and targets of commercial air-conditioned buildings in Singapore”, Final report, Centre for Building Performance and Construction, National University of Singapore (1998).

7. S.C. Sekhar, K.W. Tham, D. Cheong, N.H. Wong and Mohammed AmanUllah, “Detailed characterization of indoor volatile organic compounds (VOCs) in commercial buildings in Singapore”, Final report, Centre for Building Performance and Construction, National University of Singapore (2001).

8. K.W. Tham, “Integrated approach to indoor air quality investigation of office buildings”, In: L. Morawska, N.D. Bodfinger and M. Maroni, Indoor air − An integrated approach, 1995 edition, Elsevier, pp. 503-506 (1994).

9. X. Baur, F. Papenfub, M. Raulf-Heimsoth, V. Van Kampen and B. Kuter, “Assessment of healthy risks by air-conditioning systems in a printing office”, Proceedings of Healthy Buildings 2000, Espoo, Finland, Vol. 1, pp. 307-310 (2000).

10. “Prediction of pollutant level in the factory environment (PPLIFE)”, Ministry of Manpower, Occupational Health Department. Website downloading in June 2002. Http://www.gov.sg/ mom/wpeaw/infile/studies.htm.

11. A. Papale, F. Draicchio, T. Paola Baccolo and S. Palmi, “Allergens in indoor air: Health effects in workers of a mechanized sorting office”, Proceedings of Healthy Buildings 2000, Espoo, Finland, Vol. 1, pp. 305-306 (2000).

12. S.C. Sekhar, K.W. Tham, K.W. Cheong and N.H. Wong, “A study of Indoor Pollutant Standard Index (IPSI) and Building Symptom Index (BSI)”,


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Proceedings of Healthy Buildings 2000, Espoo, Finland, Vol. 1, pp. 145-150 (2000).

13. P.M. Bluyssen, E. de Oliviera Fernandes, L. Groes, G. Clausen, P.O. Fanger, O. Valbjorn, C.A. Bernhard and C.A. Roulet, “European indoor air quality audit project in 56 office buildings”, Indoor Air, Vol. 6, pp. 221-238 (1996).

14. Federal Standard No. 209E, Clean Room and Work Station Requirements, Controlled Environment, Office of Technical Services, Department of Commerce, Washington, DC (1999).

pollutant migration from manufacturing shop- floor … · the kanomax, climomaster, model 6521, low...

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