Airborne methylene diphenyl diisocyanate (MDI) concentrations associated with the application of polyurethane spray foam in residential construction.

The primary objectives of this study were (a) to measure potential exposures of applicators and assistants to airborne methylene diphenyl diisocyanate (MDI), (b) to measure airborne concentrations of MDI at various distances from the spray foam application, and (c) to measure airborne MDI concentrations as a function of time elapsed since application. Other study objectives were, (a) to compare the results from filter and impinger samples; (b) to determine the particle size distribution in the spray foam aerosol; (c) to determine potential exposures to dichlorofluoroethane; and (d) to measure any off-gassing of MDI after the foam had fully cured. This study was conducted during application of spray polyurethane foam inside five single-family homes under construction in the United States and Canada. Spray foam applicators and assistants may be exposed to airborne MDI concentrations above the OSHA permissible exposure limit. At these concentrations, OSHA recommends appropriate respiratory protection during spray foam application to prevent airborne MDI exposures above established limits and to protect against exposure to dichlorofluoroethane (HCFC-141b). Airborne MDI concentrations decrease rapidly after foam application ceases. The highest airborne concentrations measured after 15 min and 45 min were 0.019 mg/m3 and 0.003 mg/m3, respectively. After 45 min, airborne concentrations were below the limit of quantitation (LOQ) of 0.036-microg per sample. For samples taken 24 hours after completion of foaming, results were also below the LOQ. Approximately two-thirds of the total mass of the airborne particles in the spray foam aerosol was greater than 3.5 microns in diameter. Airborne MDI concentrations determined by filter sampling methods were 6% to 40% lower than those determined by impinger methods.

Development of a sampling and analytical method for 2,2-dichloro-1,1,1-trifluoroethane in workplace air.

The use of 2,2-dichloro-1,1,1-trifluoroethane (compound number: HCFC-123) is growing in industry as a substitute for ozone-depleting chlorofluorocarbons (CFCs). Recently, liver-related illnesses have been reported from industries handling HCFC-123. However, information on worker exposure to the material is limited, and an acceptable sampling/analytical method is not available. The aim of this study was to develop a widely applicable sampling and analytical method to determine worker exposures to airborne HCFC-123 and to evaluate the performance of the method. A solid sorbent tube, containing two sections (400 mg in the front and 200 mg in the back) of activated coconut-shell charcoal was chosen for sampling airborne HCFC-123 vapor. The breakthrough volumes were 13.6 L at 3597 +/- 210.1 ppm (with a sampling airflow rate of 0.046 L/min) and 17.0 L at 1841 +/- 4.5 ppm (with sampling airflow rate of 0.046-0.050 L/min). Samples of HCFC-123 in the charcoal tube were stable for 7 days either at room temperature or in a refrigerator and a migration occurred within 14 days at room temperature. It is recommended that the HCFC-123 sample in activated charcoal tubes be stored either at room temperature or in a refrigerator and be analyzed within 7 days. The HCFC-123 in the charcoal tubes was desorbed into dichloromethane and analyzed using gas chromatography/ flame ionization detection. The limit of detection was 0.23 mg/sample, and the average desorption efficiency was 99.0%. The total coefficient of variation was 0.060, and the method accuracy was 16.6%. In conclusion, the performance of the sampling and analytical method developed for the determination of airborne HCFC-123 concentrations was acceptable to the NIOSH sampling and analytical criteria.

The CFC challenge: chillers to replace, retrofit or ?

Health care facilities are planning for changes in regulations regarding chlorofluorocarbon-based refrigerants. These changes are imminent, leaving little time to figure out what to do with equipment using these refrigerants. This article looks at the background of the CFC phaseout program and reviews options available to engineers in assessing their equipment.