A measurement on chemicals emitted from computers and printers using test chamber method

Transcription

1 A measurement on chemicals emitted from computers and printers using test chamber method Dong Won Yoon 1, Sung Min Hong 2, Hyo Seok Kang 2, Hyo Jun Kim 2, Ji Hun Kim 2 1 Kyungwon University, South Korea 2 Research Center for Environmental System Engineering, Kyungwon University, South Korea Corresponding dwyoon@kyungwon.ac.kr SUMMARY The printers emit the chemical compound when its temperature rises during normal operations. And it primarily influenced the chemical concentrations such as formaldehyde and VOCs (Volatile Organic Compounds) in a living space. The measurements on the various types of prints from different manufacturers such as laser jet type, inkjet type were performed in emission test chambers of 1m3 and 5m3 with ventilation rate of 1.0 ACH(air change rate) supplying low-polluting clean air. During the test, chemicals emitted per PCs or Printers were analyzed on the two modes of stand-by and operation at 25 C and 50% RH. It is found that PCs and printers are a significant source of chemical emissions in small indoor environments, even with adequate ventilation. The chemicals may affect a potential health hazard for computer users. INTRODUCTION Poor indoor air quality increasing chemicals has been focused as related in sick building symptoms such as respiratory illness, itchy, eye irritation, and headaches. Exposure to pollutants in the air may cause health risk. Depending on the health effect of particular chemicals, guidelines of concentration level were established by Korean Government for avoiding the significant health effect generally associated with given concentration levels. There are many pollution sources in building and they emit hundreds of different chemicals. In indoor environment the chemicals are emitted from various kinds of products including building materials and furniture. Over the several years, emission test chamber method has been developed and several databases have been established for the information of chemicals emitted from building material only. Recently it is common for the design strategies to reduce the chemicals by selecting low emission materials and products. It would be practical data to measure the pollutants emitted from electrical equipments. Computer equipment and printers are focused on as one of the serious pollutant sources indoor. Some approaches have been performed to figure out the potentials of chemicals emitted from office equipment including computer, monitor and printer. Computers are a significant source of allergenic emissions in small indoor space like offices and individual rooms. Even with adequate ventilation, the compound may be a potential health hazard for computer users. The Purpose of this study is to clarify the emission characteristics and to determine the emission rates of chemicals on the computer set and printer.

2 METHODS It is known that the perceived indoor air quality caused by VOCs emitted from new building materials generally decrease over time in concerns. Computer set including a monitor and a printer can emit the VOCs during operation continuously. Some questions often arise that how much will the VOCs emit and how the emission rate change with different mode of operation. The measurements of VOCs and HCHO emission from the computer and printer were conducted using the test chamber method. The chemicals were measured the variation of the emission rates with two different stages of usages. One is for the standby mode, which is not operating the PC but emitted the chemicals continuously, and the other is for the condition of operating mode, of which temperature is goes up with chemicals emitted intensively during operation. Several cases were tested how the profiles of emissions are varied with products from different manufacturers. Test Chamber and Equipments Two systems of emission test chamber were built for measuring emission rates from the computers and printers. One is prepared 1m 3 (W 1m x L 1m x H 1m) in scale of air volume for measuring relatively small products like computer sets, which is combined with double chamber system as outer and inner chamber. The buffer zone is realized between two chambers for precisely controlling environmental parameters of temperature, humidity and pressure differences. The other is a large scaled test chamber with volume of 5 m 3 for large products, which is constructed as single chamber type and using emission test for printers. Both of two inside chambers are constructed with stainless steel for confirming not emitting any chemicals themselves. Environmental conditions of the chamber, such as temperature, relative humidity, air change rate and air velocity could be precisely controlled at setting points. In this measurements, they were controlled to the temperature of 25 o C o C, relative humidity of 50+5% RH, ventilation rate of air exchange per hour and air velocity of m/sec. The tests were performed for measurement of formaldehyde and VOCs from the products under designed conditions to simulate the situations of products use indoor. Fig. 1 Diagram of the 1 m 3 test chamber Test Products Desktop computer sets with keyboard and monitor were selected for the test of formaldehyde and VOCs emitted. Three laser printer sets from different manufacturers and one ink jet

3 printer were selected for the measurements. They are all new products which were ordered through a retail distributor directly to ensure the brand new and ordinary shipping procedures. The outlines of tested samples are shown in table 1. Figure 2 figures of test chamber facilities both of 1 m 3 and 5 m 3 Table 1. Test samples of measurement for determining emission rates Test Sample Composite of the Samples Remarks Computer Set A Computer + Keyboard + TFT Monitor Desktop Manufacturer 1 Computer Set B Computer + Keyboard + TFT Monitor Desktop Manufacturer 2 Computer Set C Lab-top computer + TFT Monitor Lab-top Manufacturer 1 Printer A Laser / Black and white Manufacturer 2 Printer B Laser / Color Manufacturer 2 Printer C Laser / Color Manufacturer 1 Printer D Ink jet / Color Manufacturer 1 Protocol for Chamber Test Preparation of the test chamber Before placing the test product in the chamber, background air samples were collected from the chamber to be assured the test condition. And adjustment was performed for the air flow, temperature, and relative humidity to assure the standard test condition. And then background samples were collected for analysis of formaldehyde and VOCs. After every emission test, the camber were cleaned with distilled water and baked out at 100 o C with purified air. After confirming the background level should not exceed the standard background levels, the test product was to set placing and test was started with test procedure. Sampling and analysis method Sample products are tested for emissions of pollutants using stringent environmental chamber test protocols. Emission concentrations were determined by placing the test objects in the chamber under specified test condition, then measuring chamber concentration of HCHO and VOCs with selected time intervals. Product emission factors were calculated from the chamber air samplings. A typical test period is 8 hour with measurement time at 2, 4, 6, and 8 hour. Some products like printers may require a specified procedure during test period to accurately define the emission profile. Sampling of Volatile Organic Compounds Sampling VOCs were collected on sorbent cartridges (TA tubes). VOCs trapped on the cartridges were thermally desorbed then analyzed by GC/MS. Testing results of these analyses were used to estimate both of TVOCs and individual VOC concentration. Detailed procedures for sampling and analyzing the chemicals with chamber test method and TA tube cartridges described in ISO , 7, 9

4 Sampling of Formaldehyde Air samples for formaldehyde were collected on 2,4- dinitrophenylhydrazine(dnph) coated silica gel cartridges with ozone scrubbers. The DNPH derivatives on the cartridges were eluted with acetonitrile and analyzed by high performance liquid chromatography(hplc) with ultraviolet(uv) detection. Air Samples from chamber Calibrated air pumps located outside the chamber were used to pull chamber air through sampling cartridges mounted in the chamber ports (couples of two sampling ports) installed both as one is for the center of the chamber and the other is for the outlet of the exhaust duct. Calculation of emission factor An emission factor is the amount of chemical that is emitted from a product at selected point in time. It is normalized to a particular size or unit of the product. For most building material, the emission factor is usually measured for exposed unit area of the product as square meter. However in this study, a product test reports the emission factor explain test results relative to a complete unit (µg/unit*hr). If the product is not constantly emitting pollutants, the emissions are decreasing gradually over time, the emission factor is a qualitative estimate of emissions release at a particular point in time. The emission factors of chemicals were calculated by the following equation. C t : Chemical concentration at time t ( mg / m3 ) Ctb,t : blank concentration at time t ( mg / m3 ) n : ventilation rate (ACH/h) Q: Airflow rate in chamber ( m3 /h) V : Air volume of test chamber ( m3 ) RESULTS Ventilation Rate in test chamber In order to evaluate the performance of ventilation in test chamber, air change rate, ventilation effectiveness and age of air were measured at different location using concentration decay method with SF6 as tracer gas. Sampling tracer gases at the center point, and upper zone and lower zone in the chamber were performed with controlled airflow rate at 0.5 ACH/h, 1.0 ACH/h and 2.0 ACH/h. Table 2 shows the profiles of ventilation rate and age of air at the measuring points in 5 m 3 chamber. Air change rates were pretty much similar to the setting values at the center point for all cases. It shows the air change rates were controlled within 10% at every location in the chamber Computer set and Chemical emissions Some chemicals composed electronic equipment that have recently received attention with chemical component of the plastic case and printed circuit board. In order to fully understand how a product is going to contribute to indoor concentrations of pollutants, it is necessary to know a product's emission rate profile, or how the product's emission rates change over time. During the test period, multiple pollutant measurements are performed which are then used to

5 calculate the product's emission profile over time. Fig. 4 shows TVOC profiles of emission from the computer set over time measured at center and outlet in the chamber with its operation. TVOC concentration at the center point measured much higher than the outlet point. TVOC concentration indicated the peak after 4 hr from the start of measurement, and decreased gradually over time. Some of individual VOCs were detected. Emissions of toluene, ethylbenzene and xylene in VOCs as caused for health risk compound were emitted with its operation as shown in table 4. SF6 concentration [ppm] :00 19:00 20:00 21:00 22:00 23:00 0:00 1:00 2:00 Time [h] Figure 3. Profiles of SF6 concentration Table 2. Ventilation rates in 5 m3 chamber Air Flow Sampling points ACH/h Ventilation Efficiency[%] Age of Air [min] Air Change Rate Upper Zone ACH/h Center [l/min] Lower Zone Air Change Rate 1.0 ACH/h [l/min] Air Change Rate 2.0 ACH/h [l/min] Upper Zone Center Lower Zone Upper Zone Center Lower Zone Fig. 5 and Fig. 6 shows the profiles of TVOC and formaldehyde concentration emitted from tested computer sets. Emission rates of chemicals from desktop computer indicated much more higher than those of lab-top computer set. It may be possible to assume that the emission rates could be higher from the computer due to the bigger size and more consumption of electricity emitted much VOCs. Emissions of HCHO concentration ranged from 2 µg/m 3 to 44 µg/m 3 were not much higher relatively. TVOCs (mg/m3) hr 4hr 6hr 8hr 10hr Measureing time outlet center Figure 4. TVOC profiles of chemicals Table 3. Individual VOC emitted from computer set Compound Name 2 hour 4 hour 6 hour 8 hour 10 hour Outlet Center Outlet Center Outlet Center Outlet Center Outlet Toluene Ethylbenzene p-xylene o-xylene Benzene,1,3,5- trimethyl- Benzene,1,2,4- trimethyl Unidentified TVOC[ mg / m3 ] TVOC ( mg /unit h) Computer A Computer B Computer C Monitor Computer body HCHO ( mg /unit h) Computer A Computer B Computer C Moniter Computer body Figure 5. TVOC profiles from PC sets Figure 6. Formaldehyde profiles from PC sets

6 Printers and Chemical emissions The chemical emissions printers can result from plastic construction materials, circuit boards, the inks and toners, papers, coatings on transparencies. Many of these chemical emission profiles show decreasing with usage of the product. But emissions from the printers as the harmful pollutants is not decreased much during the operation, because the VOCs emissions from the laser printer caused by heating up the drum and toner at 160 o C for compress toner on paper with chemical components. However, the result in the mechanical operation of printing procedure emitted harmful chemicals to indoor environment. During the measurement of printers, chamber was controlled at 25 o C, 50% RH and 1.0 ACH/h. Temperature and humidity of the chamber goes up to 48 o C and 57% RH due to generate heat and moisture from the printer procedure. Fig. 7 shows the profiles of chemical emission from the printers. The emission rates of the TVOC concentration ranged from 0.31 mg/m 3 to 8.00 mg/m 3 at the standby mode. Some printers emit still high concentration of chemicals during standby mode and ready mode without any operation. On the operation, the emission rate of chemicals goes up to the mg/m 3. Even though a similar printing speed and quality, Printer B emits 5 times more chemicals comparing to those of printer A. Laser printer C of B&W emits TVOC to 3.12 mg/m 3 during operation and still highly emits the chemicals on the standby mode. Inkjet printer also emits relatively high during operation. Table 8 indicates the individual VOCs from the printers. Individual organic compound of benzene, toluene, ethyl-benzene, xylene, styrene were dominant. It could be possible that laser printer has been associated with building-related symptoms and health effects due to the release of chemical gases during operation. TVOC ( mg /unit h) Printer A Printer B Printer C Printer D HCHO ( mg /unit h) Printer A Printer B Printer C Printer D Ready mode printing Figure 7. TVOC profiles from printers Ready mode printing Figure 8. Formaldehyde profiles from printers Table 4. Individual VOCs profiles emitted from different types of printers Laser Printer A(color) Laser Printer B(color) Laser Printer C(B & W) Inkjet Printer Standby(1hr) On printing Standby(1hr) On printing Standby(1hr) On printing Standby(1hr) On printing Benzene Toluene Ethylbenzene p-xylene Styrene o-xylene Unknown

7 a) Chemicals from Printer A b) Chemicals from Printer B Figure 9. Examples of Gas Chromatogram for the different printers.

8 DISCUSSION Though none of these chemicals from computers and printers is likely to be measured in quantities that would exceed any established workplace health and safety limits, the unknown factor is how some of these chemicals may interact with each other to cause problems many years in the future. In addition, there are no established health and safety limits for exposure to chemicals by electronic devices exactly right now. Computer with laser printer has been associated with building-related symptoms and health effects due to the release of chemicals during operation. These emissions can result from the inks and toners, papers, plastic construction materials, circuit boards. Many of these chemicals will decrease with usage of the product such as computers. Laser printers in particular have been associated with headaches, mucous irritation and eyes and nose irritation As a result, computers should be placed in other areas of the home in order to minimize health risk in the bedroom. ACKNOWLEDGEMENT The authors thank the Korea Ministry of Environment and Korea Institute of Environmental Science and Technology for the support in this study(environmental Technology development Project for Next Generation, ) REFERENCES 1. Yoon, D.W The Measurement of chemical emission from home appliances and furniture, Seoul: Report for Korea Ministry of Environment. 2. Yoon, D.W The Establishing the Large test Chamber System to detecting the chemical emission from the various products. Seoul, Research Report for KIEST in Korea. 3. ISO : Determination of VOC emission: emission test chamber/test cell method, procedure for sampling, storage of samples and preparation of test specimens. 4. GreenGuard. 2005: Office Furniture Test Requirement Specification For The GreenGuard Indoor Air Quality Certification Program. 5. ENV (CEN): Building products, determination of the emission of volatile organic compounds-part1: Emission test chamber method 6. RAL-UZ85: BAM-2005: The Method For The Determination Of Emission From Hardcopy Devices 7. Standard ECMA-328: Detection and Measurement Of Chemical Emission From Electronic Equipment 8. JEITA(Japan) 2006: VOCs Guidelines for personal computer.