Respirator Cartridges Research Articles

Respirator cartridge efficiency studies: VII. Effect of relative humidity and temperature.

Cartridge service life is not appreciably affected at relative humidities below 50%. However, performance is severely compromised when the humidity exceeds 65%. Experimental values are compared from those calculated from the adsorption isotherm, Mecklenburg and modified Wheeler equations. Calculations indicate that temperature does not play a significant role in service life predictions.

Respirator cartridge efficiency studies: VI. Effect of concentration.

The service life of organic vapor cartridges was determined for ten vapors at concentrations between 50 and 3000 ppm. The breakthrough time (tb) conformed to the empirical expression tb = aCf, where C is the concentration in ppm and a and be are constants. The average value for b at 10% breakthrough was -0.67 +/- 0.17. The service life is inversely proportional to flow rate for acetone and benzene.

Preparation of mixtures of humidified air with CO, SO2, NO2, NH3, NH2CH3, Cl2, and HCl to measure respirator cartridge and canister service life.

Four systems have been fabricated to measure the effective service life of respirator cartridges and canisters. The four systems employ carbon monoxide, sulfur dioxide/nitrogen dioxide, ammonia/methylamine, and chlorine/hydrogen chloride as contaminants. Each system produces test concentrations in the low percentage range (typically 0.05 to 3.0%) at flow rates of 32 and 64 liters/min and at relative humidities between 20 and 95%. Suitable anlyzers have been provided to measure the downstream concentration from 1 to 500 ppm as a function of time. Holders have been designed to accommodate the wide size variation of commercially available cartridges and canisters.

Respirator cartridge efficiency studies. V. Effect of solvent vapor.

We have determined the service lives of organic vapor respirator cartridges for 121 solvent vapors and gases including aromatics, alcohols, acetates, alkanes, ketones, amines, and chlorinated materials. We passed the vapor and air mixtures through the cartridges and monitored the downstream concentration with a flame ionization detector (FID). Monitoring continues until the cartridge is completely saturated. We compared breakthrough times to values calculated from the adsorption isotherm and Mecklenburg equation and obtained reasonable agreement. In general, the activated carbon has greater affinity for the less volatile materials. Also, the higher the boiling point of the solvent, the greater is the weight of solvent adsorbed. Water vapor, in general, decreases the amount of solvent vapor adsorbed, especially of the more volatile solvents and those soluble in water. The effect of concentration on breakthrough time was briefly investigated and found to conform to the basic Freundlich equation.

Respirator cartridge filter efficiency under cyclic-and steady-flow conditions.

Respirator filter cartridges are routinely tested under steady-flow conditions to provide a basis for predicting their future performance under cyclic-flow breathing conditions. Tests were performed to define aerosol penetration through respirator filter cartridges under both cyclic and steady flow. A breathing pump was used to simulate different human breathing patterns. Steady-flow conditions were identical to those recommended by the U.S. Bureau of Mines for permissibility tests of respiratory protective devices. Solid monodisperse polystyrene latex aerosols ranging from 0.176 to 2.02 μm in size and liquid monodisperse 0.3-μm dioctyl phthalate were used as the test aerosols. Sampling during cyclic flow was performed without altering the flow pattern through the respirator cartridge. Steady- and cyclic-flow experimental data are compared as a function of aerosol size, breathing pattern, and aerosol type. Theoretical steady-flow aerosol penetration is compared to experimental cyclic-flow data.

Service livers of respirator cartridges versus several classes of organic vapors.

The effective service life of chemical respirator cartridges varies with the organic vapor absorbed on the charcoal. Life versus various compounds was determined by exposing chemical cartridges to vapors, some of which were of fairly high toxicity. An apparatus was assembeld to produce dynamic mixtures containing 1000-ppm concentrations of organic vapors. The effluent was continuously monitored to determine cartridge service life using hydrogen flame ionization detection. Service Life depends on the compound to which the cartridge is exposed. Breakthrough patterns for several compound classes may serve as a rough guide for untested compounds within a homologous series.

Respirator cartridge efficiency studies. IV. Effects of steady-state and pulsating flow.

The service life of organic vapor respirator cartridges has been evaluated for steady-state and pulsating flow rates; a mechanical breathing simulator was used to evaluate the pulsating flow rates. Two types of cartridge have been tested at work rates of 0, 208, 415, 622, 830, and 1107 kg-m/min and their equivalent respective steady-state flow rates of 14.0, 20.6, 29.8, 36.9, 53.3, and 71.4 liters/min. Cartridge break-through characteristics were recorded with both types of flow for several solvents at 1000 ppm and 0%, 50%, and 80% relative humidity. No significant differences were observed between the steady-state and pulsating flows, even at the highest work rate and humidity conditions. The effective service life appears to be inversely proportional to the flow rate at a given concentration.

Respirator cartridge efficiency studies. I. Experimental design.

This is the first in a series of papers dealing with the determination of the service life of respirator cartridges in atmospheres containing organic vapors. A testing facility to produce test atmospheres of known composition has been built. The cartridges are placed in a specially designed and constructed holder; and breakthrough times are determined by measuring the upstream and downstream concentrations, by means of dual flame ionization detectors. The breakthrough characteristics can be ascertained by using either a steady-state condition or a cycling flow produced by a breath simulator. A standard cartridge has been designed to evaluate system performance and to periodically check the system for reproducibility. Parameters to be studied include the effects of organic compounds, concentration, work rate, temperature, and relative humidity on cartridge efficiency.

Respirator cartridge efficiency studies. II. Preparation of test atmospheres.

A system for determining the breakthrough characteristics of respirator cartridges has been assembled that continuously produces known concentrations of solvent vapor in humidified air. Concentrations from 1 ppm to several percent can be generated in airflows of 20 to 250 liters/min. The humidity can also be selectively adjusted from 1 to 95%. The contaminant gas concentrations on either side of the respirator cartridge are monitored continuously by two flame ionization detectors. Concentrations of several parts per million are routinely detected. The airflow rate, humidity, and gas concentrations are recorded continuously on strip recorders for easy display and comparison of data.

Sorbents and catalysts for respirator cartridges and gas mask canisters.

Abstract The sorbent materials presently used in respirators include activated charcoal, soda lime, silica gel, molecular sieves, alkaline silicates, and impregnated charcoals. Design parameters of the sorbent bed which must be considered are baffling, tension on layers, packing uniformity, packing density, and both velocity and depth of bed. The selection of a sorbent depends on two groups of factors: (1) protection provided to the wearer, integrity of properties, and comparability with proposed use; and (2) subcritical factors such as cost, bulk, weight, and ease of manufacture. To be effective, the best respirator must still be worn and maintained properly.