New Respiratory Protection Standard – Cartridge Change-Out Schedules

What Does the Standard Require?

CCR Title 8, Section 5144 c1e requires that employers include, as part of their written respiratory program, procedures and schedules for cleaning, disinfecting, storing, inspecting, repairing, discarding, and otherwise maintaining respirators.   The new Standard also requires in Section 5144d3C2b that, if an end of service life indicator (ESLI) is not available or is not appropriate for conditions in the employer's workplace, that the employer has the responsibility to implement a change schedule for canisters and cartridges that is based on objective information or data that will ensure that they are changed before the end of their service life .  The employer is also required to describe in the written respiratory program the information and data relied upon and the basis for the canister and cartridge change schedule and the basis for reliance on the data. 

How Do We Comply?

It is essential for CSRMA members to characterize the nature and magnitude of employee exposures to respiratory hazards before selecting respiratory equipment. Paragraph (d)(1)(iii) of the final rule requires the employer to identify and evaluate the respiratory hazard(s) in the workplace. Employers must make a "reasonable estimate" of the employee exposures anticipated to occur as a result of those hazards, including those likely to be encountered in reasonably foreseeable emergency situations, and must also identify the physical state and chemical form of such contaminant(s). The final rule does not specify how the employer is to make reasonable estimates of employee exposures for the purposes of selecting respirators.

When must an employer conduct an exposure assessment?

 When employees are exposed to a respiratory hazard and/or are required to wear respirators. Examples of when assessments should be considered may include but are not limited to:

• When OSHA has a substance specific standard(e.g. lead, methylene chloride).
• When employees notice symptoms (e.g. irritation, odor) or complain of respiratory health effects.
• When the workplace contains visible emissions (e.g. fumes, dust, aerosols).

 

What is the identity and nature of the airborne contaminant?

Specific characteristics of the airborne hazard must be established in order to select an appropriate respirator.

• Is the airborne contaminant a particulate (dust, fumes, mist, aerosol) or a gas/vapor?
• Is the airborne contaminant a chemical and are material safety data sheets available?
• Is the airborne contaminant a biological (bacteria, mold, spores, fungi, virus)?
• Are there any mandatory or recommended occupational exposure levels for the contaminant?

 

How much employee exposure is there in the workplace?

The final rule permits employers to use many approaches for estimating worker exposures to respiratory hazards.

• Sampling - Personal exposure monitoring is the "gold standard" for determining employee exposures because this is the most reliable approach for assessing how much and what type of respiratory protection is required in a given circumstance.

o Sampling should utilize methods appropriate for contaminants(s).

o Sampling should present the worst case exposures; or

o Sampling should represent enough shifts and operations to determine the range of exposure

 

• Objective Information - Employers may rely on information and data that indicate that use or handling of a product or material cannot, under worst-case conditions, release concentrations of a respiratory hazard above a level that would trigger the need for respirator use or require use of a more protective respirator.

o Employers can use data on the physical and chemical properties of air contaminants, combined with information on room dimensions, air exchange rates, contaminant release rates, and other pertinent data, including exposure patterns and work practices, to estimate the maximum exposure that could be anticipated in the workplace.

o Data from industry-wide surveys by trade associations for use by their members, as well as from stewardship programs operated by manufacturers for their customers, are often useful in assisting employers, particularly small-business owners, to obtain information on employee exposures in their workplaces.

 

• Variation - Employers should account for potential variation in exposure by using exposure data collected with a strategy that recognizes exposure variability, or by using worst-case assumptions and estimation techniques to evaluate the highest foreseeable levels to which employees may be exposed. The use of safety factors may be necessary to account for uneven dispersion of the contaminant in the air and the proximity of the worker to the emission source.

Respirator cartridges don't last forever!  A cartridges useful service life is how long it provides adequate protection from harmful chemicals in the air.  The service life of a cartridge depends upon many factors , including environmental conditions, breathing rate, cartridge filtering capacity, and the amount of contaminants in the air.   The specific recognized factors that can reduce cartridge service life include:

Worker Exertion Level: A worker breathing twice as fast as another will draw twice the amount of contaminant through the respirator cartridge.

The service life of a cartridge or canister respirator is dependant upon the total amount of contaminant captured by the adsorbant. The total amount of captured contaminant is directly related to the work rate or breathing rate; i.e. a worker breathing twice as fast as another will draw twice the amount of contaminant through the respirator cartridge. Most of the cartridge studies have used a breathing rate, 50-60 liters per minute, which approximates a high end of moderate workrate. For workrates that exceed this level (e.g. heavy shoveling, running) a correction factor may need to be applied or taken into account when determining a service life.

Respirator Cartridge Variability: Some cartridges contain more activated charcoal than another.

The service life of a respirator cartridge is directly related to the amount of active material in the cartridge. For instance, most dual cartridge organic vapor respirators contain between 35-50 grams of activated charcoal in each cartridge. If the specific cartridge being evaluated can be reproducibly determined to have a certain amount of active material, then modifications to the service life may be justified. Information on the specifications for the cartridges can be obtained from the manufacturers.

Temperature:The hotter it is, the shorter the service life.

High temperatures can adversely affect the adsorptive capacity of respirator cartridges and canisters. The high temperature may act by thermally loosening the attractive forces that make adsorption happen or may act in concert with humidity by increasing the moisture carrying capacity of air. This latter mechanism may represent the greatest likely effect on service lives of cartridges. Temperature effects alone have been reported to reduce the service life 1-10% for every 10 degrees Celsius rise depending on the specific solvent (Nelson, et. al., 1976). Corrections to cartridge estimated service life for this effect alone is probably not necessary under normal working temperatures.

Relative Humidity : Water vapor will compete with the organic vapors for active sites on the adsorbent.

Relative Humidity is a measure of the amount of water vapor the air will hold at a specified temperature and is expressed in percentage values. Since warmer air will hold more water than colder air, the same relative humidity at a higher temperature represents a significantly greater amount of moisture. High relative humidity is a significant negative factor in the capacity of organic vapor cartridges since the large quantity of water vapor will compete with the organic vapors for active sites on the adsorbent. Most of the laboratory work determining adsorbent capacity has been performed at a low relative humidity of 50% at approximately 70 degrees F.

If the actual use of the organic vapor respirators will take place in a significantly more humid environment, then a safety factor may need to be applied or taken into account when determining a service life. The exact magnitude of the humidity effect is a complex determination dependent in part upon chemical characteristics and concentrations of both the contaminant and the water vapor. Based upon relatively few studies, a reduction by a factor of 2 in the cartridge service life originally estimated based upon 50 % relative humidity, may be made when the relative humidity reaches 65% (Nelson, et. al., 1976; Werner, 1985). If the relative humidity exceeds 85%, the user should consider experimental testing or another method to more specifically determine the service life. Mathematical modeling may be an appropriate, albeit complex, approach to predict the effect of humidity at various chemical concentrations (Wood, 1987; Underhill, 1987).

Multiple Contaminants : Predictions should be derived from the least well absorbed compound.

Multiple contaminants introduce a great deal of variability into the prediction of service life for respirator cartridges. Much of the laboratory testing and the mathematical models have utilized a single contaminant to determine service lives. Only a limited amount of multiple contaminant situations have been studied and reported in the literature (e.g.Yoon, 1996; Jonas et. al., 1986). Cartridge service life for mixtures of compounds with significantly different chemical characteristics are probably best determined by experimental methods. Predictions based upon models without experimental data should probably be very conservative and ascribe the service life derived from the least well absorbed compound to the total mixture concentration in terms of parts per million. The displacement of a less well adsorbed compound by a more highly adsorbed one may alter the actual service life from the estimated one in some cases.

 A safety factor should be applied to the service life estimate to assure that the change schedule is a conservative estimate. 

How can we estimate the service life of a particular cartridge?

If you know what the chemical is and how much of it you are exposed to, then you are ready to estimate how long your respirator cartridges will work and apply the safety factor. FedOSHA has identified three valid ways for you to accomplish this task: (a summary of items to bear in mind for each method is provided at the end of this Bulletin)

1.  Conduct experimental tests:

This is probably the best way to determine the service life for multiple chemicals or specific conditions.  Additional information on this can be found at http://www.osha-slc.gov/SLTC/respiratory_advisor/testing/testing.html

2.   Use the manufacturer's recommendation:

Chemical and respirator manufacturers may be able to provide an estimate based upon their own expertise and testing data. For a listing of manufacturers, go to the Industrial Safety Equipment Association's buyer's guide at http://www.safetycentral.org/isea/index.html .

3.   Use a math model:

Mathematical models have been used to predict the service life of organic vapor cartridges when used for protection against single contaminants.  Using an equation developed by G. Wood, some service lives have been pre-calculated and are presented in a table that can be found at

http://www.osha-slc.gov/SLTC/respiratory_advisor/wood_table/wood_table.html .   The service life estimate should be reduced by some safety factor to give a change schedule that is documented in the written respiratory program.

 

Summary of Methods to Estimate Cartridge Service Life

MethodKeep In Mind…Conduct experimental tests

There is no widely accepted, standard protocol for performing service life testing.

The EPA has published draft Interim Recommedations for cartridge testing.

A field testing approach is provided by Cohen, H. J., Development of a Field Method for Calculating the Service Lives of Organic Vapor Cartridges – Part IV. Results of Field Validation Trials, American Industrial Hygiene Association Journal, (1991), pages 263-270.

Ideally, respirator cartridges should be tested under worst case conditions either in the or in the laboratory.

The determination of breakthrough from workplace testing does not require the determination of the full breakthrough curve for the respirator cartridge.Use the manufacturer's recommendationKeep In Mind Manufacturers are likely to possess the most accurate data for their own respiratory products.

However, the manufacturer may not have tested the respirator with the chemicals that you work with, and therefore may not be able to offer a reliable recommendation. Use a math modelThe math models are usually only directly applicable for single contaminant exposures. 

Multiple contaminant situations may lean towards using other methods of deriving schedules orincreasing the use safety factors.

The Wood Math Model is just one equation you can use.  Also, because it is a predictive type of model (as opposed to a descriptive type), it should not be relied upon without some experimental confirmation of the calculation or use of appropriate safety factors

Please Don't Forget to Complete and Return Your Y2K Survey To David Patzer