A testing protocol for organic vapor respirator canisters and cartridges.
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Air Pollutants, Occupational↗
Biomedical subjects
M W Ackley
Publications and source records attributed to M W Ackley.
Chemical cartridge respirator performance: 1,3-butadiene.
The chemical 1,3-Butadiene recently has been classified as a potential occupational carcinogen; subsequently, a reduction in the 8 hr TWA from 1000 ppm to 10 ppm has been proposed. Substantial quantities of 1,3-Butadiene are produced annually for use in the manufacture of a variety of rubber compounds, foams, resins and chemicals. Existing process environments may present a potential health hazard under the proposed standards, and the need for proper respiratory protection is evident. As a result, the performance of Scott organic vapor (642-OV), organic vapor/acid gas (642-OA) and acid gas (642-AG) twin cartridges has been determined for 1,3 butadiene. A cartridge test system was developed to generate challenge concentrations of 100 ppm and 1000 ppm; an infrared analyzer was used to measure breakthrough at 10 ppm. The residence time modeling concept developed previously was used to produce the performance characteristics for three types of activated carbon for residence times of 0.1 less than or equal to tau less than or equal to 1.0 sec. Kinetic adsorption capacities and adsorption rate constants were computed from this data, and cartridge performance also was predicted. The twin cartridges tested demonstrated reasonable adsorption capacity for 1,3 butadiene. Cartridge service life was found to be inversely proportional to airflow rate; it was reduced at elevated temperature and humidity conditions. Breakthrough times were approximately three times longer at 100 ppm than at 1000 ppm. When clean air was drawn through cartridges saturated with 1000 ppm 1,3 butadiene, desorption occurred readily. The rate of desorption and the peak concentration were found to be dependent upon the temperature, humidity and degree of saturation.
Adsorption↗
Residence time model for respirator sorbent beds.
An experimental bed residence time model has been developed to characterize the performance of sorbent beds in removing gaseous contaminants. This model is applicable to both adsorption and chemisorption processes. The fundamental characteristics produced can be used to predict the performance of respirator cartridges and canisters over a wide range of operating conditions. A family of performance curves can be constructed for a specific product type for application in determining minimum service life and renewal frequency. This model is described in terms of a dynamic sorption concept, and is demonstrated using ASC I carbon and sulfur dioxide in air at concentrations of 500 ppm, 1000 ppm and 5000 ppm. Adsorption data is also provided for carbon tetrachloride. The effects of bed depth and superficial velocity reduce to a unique relationship between breakthrough time and bed residence time. The influences of moisture, concentration and heat transfer at the walls of the sorbent containment have all been investigated in this study. The dynamic sulfur dioxide capacity of ASC I carbon was found to increase significantly at increasing levels of adsorbed moisture for decreasing sulfur dioxide concentrations. The interrelation of moisture and concentration of sulfur dioxide produces a secondary removal mechanism for which the chemistry is briefly described.
Adsorption↗
Hydrogen sulfide generation and detection system.
A test system has been devised for generation and measurement of hydrogen sulfide/air mixtures. Such a system has numerous applications, including toxicology studies, detector badge and tube evaluation, sorbent capacity measurements, and respirator cartridge or canister breakthrough testing. The system in this study utilizes an HNU photoionization analyzer for detection of H2S concentrations of 1.0 ppm to 26.0 ppm. Generation techniques for these low concentration levels, and also for much higher H2S concentrations, have been described. Special consideration has been given to H2S permeation of transfer tubing, and to the effects of water vapor interference upon the analyzer.
Air Pollutants↗
Paint spray tests for respirators: aerosol characteristics.
Liquid paint is sprayed from an atomizing nozzle to form an aerosol for testing paint spray respirators. The generated aerosol conditions are dependent upon liguid properties, spray-nozzle flow conditions and droplet evaporation. A technique was developed for controlling the aerosol concentrations reliably. Particle-size distributions of lacquer and enamel have been measured. The lacquer distribution was found to be multi-modal. Aerosol concentration dradients arise when the nozzle is not properly positioned. Filter loading resistance is significantly affected by these concentration variations. With regard to selection of standard aerosol test be improved by modifying the current NIOSH criteria to include a description of the particle-size distribution, a more precise definition of the paint and paint thinner chemical compositions, and a narrower concentration range.
Aerosols↗