When using air-purifying respirators, site conditions such as temperature, humidity, work rate and altitude all affect the service life of chemical cartridges. With temperature being a primary concern during summer months, it is important to understand the implications for users of APR chemical cartridges.
In most cases, the service life of a chemical cartridge decreases with elevated site temperatures. Gas and vapor contaminants are adsorbed physically or chemically onto sorbent material in the cartridge. As temperature increases, the volatility for a contaminant increases, making it less “attractive” to the sorbent material, resulting in earlier breakthrough of the contaminant. The extent to which the service life decreases is dependent on the temperature, contaminant and cartridge type.
Using cyclohexane as an example, service life of a typical APR cartridge may drop by roughly 20 percent if the temperature increases from 77° F to 104° F. The effect on service life is generally more dramatic with higher volatility chemicals (those with low boiling points and lower molecular weight). In the case where adsorption of a contaminant depends on reaction, the effect of temperature on service life becomes more complicated. Nevertheless, it is rarer for the service life to increase with temperature.
Be mindful of diurnal temperature changes and movement from cold to hot areas in a facility, as this may cause “desorption,” which is breakthrough due to a contaminant previously adsorbed being released from the sorbent. Though desorption is generally less common, it is likely that the effective service life of the cartridge will be less in the hotter environment.
When developing change-out schedules for APR cartridges using objective data, calculations or manufacturer service life tools, make sure to include corrections for humidity, breathing rate, altitude and temperature. Manufacturers should also be consulted for specific situations when assistance is needed.
Last, temperature should always be a consideration when conducting site hazard assessments. Temperature will influence the amount of chemical vapor in the air, its mixing properties and potentially its form. In colder conditions, the overall vapor concentration may be lower, but aerosol mists may be present that require a particulate filter or combination filter with particulate protection to mitigate.
To summarize, temperature can have a moderate to significant impact on the service life of APR chemical cartridges and should be considered as part of the exposure assessment during the development of a respiratory protection plan.