Assessing employee exposure to hazards is one of the most important elements of the respiratory selection process and can be difficult to evaluate. First, you need to identify the source of the hazard and determine the type of hazard. Is the hazard a particulate, gas, vapor or combination of types?
Once you know the hazard, you can determine the airborne concentrations of the hazards and compare them with exposure limits (PEL, REL, TLV, IDLH) and OSHA substance-specific standards. To determine the airborne concentration for an employee, you could monitor his or her exposure utilizing a personal monitor that the employee would wear for a full work shift to determine the time-weighted average (TWA). OSHA also has monitoring requirements for certain substance-specific chemicals, like those found in 1910.1052 for Methylene Chloride.
You also need to determine the physical and chemical properties of the hazard; this is helpful for identifying such things as flammability. You need to understand the physiological effects of the hazard and be able to explain this to the employee during training.
If the hazard is a gas or vapor, you should determine if it has adequate warning properties. Examples of warning properties could be a pungent odor or an irritation to the eyes.
Now that you have the employee's hazard exposure and determined the exposure limit for the given hazard, you can calculate a hazard ratio. The hazard ratio is the employee's hazard exposure divided by the exposure limit (PEL, REL, TLV). The hazard ratio is used to determine the level of protection required for a specific application.
KNOW THE WORK AREA
It's important to know what, if any, added safety hazards the employees may face while wearing respiratory protection. For example, are there moving parts that could create a safety hazard or does the work area restrict access or movement? How far is the work area from fresh air? Is any additional personal protective equipment (PPE) required that could affect the fit or performance of the respirator?
Furthermore, you should determine if there are any additional demands placed on the employees that would prevent you from selecting a certain type of respirator.
Ask yourself these questions: How long will employees be required to wear respirators? What are the environmental stresses (heat, humidity, cold) that could add to the hazard? What would the work rate be for the particular task (light, moderate, heavy)? Are the employees required to communicate during the task? Does the employee need prescription eyewear to perform the job duty?
KNOW THE AVAILABLE RESPIRATOR OPTIONS
There are various types of respirators to choose from, each designed to provide a specific level of protection for a given hazard. Some respirator examples include self-contained breathing apparatus (SCBA), powered air-purifying respirators (PAPR) and air-purifying respirators (APR).
Each type of respirator has been given an assigned protection factor (APF) by OSHA that can be found in Table 1 of the 1910.134 Respiratory Protection Standard. The assigned protection factor is the minimum amount of protection provided by a respirator type.
It's important to evaluate the limitations of the respirators during the selection process.
Some respirators can be used in more hazardous environments than others; for example, an APR should not be used in an oxygen-deficient atmosphere, but an SCBA could be appropriate.
OSHA 1910.134 Respiratory Protection Standard requires that the respirator selected be NIOSH-certified.
MAKING THE CORRECT SELECTION
Now that you know what your hazards are, what the work environment is, what the demands are that employees face and what respirator options are available, you can use this information to select the appropriate respiratory protection.
The hazard ratio determined during the hazard assessment phase now can be used in selecting the respirator. If the hazard ratio is less than the APF, then the respirator assigned to that APF is appropriate for the hazard.
Here are a few factors to take into account when making the final respirator selection:
- Identify the contaminant (gas, vapor, particulate)
- If gas or vapor, is there a chemical cartridge suitable for the contaminant?
- Determine concentration of contaminant, oxygen content and contaminant levels
- Determine the hazard ratio and compare it to the APF
- For gas and vapor, determine end of service life indicator (ESLI) or change-out schedule based on service life
- If there is a particulate filter, deter- mine filter efficiency and series required (N, R, P)
- Assess workplace conditions for specific selections
Using these factors as guidance in addition to using tools, such as the NIOSH Respirator Decision Logic, can get you started, but it's important to note that not all hazards and applications are the same. A proper hazard assessment should be made prior to the respiratory selection process and any time a hazard or application changes. Now you know.
Jenny Cornagie is air purifying product manager for Scott Health and Safety, Monroe, N.C. (http://www.scotthealthsafety.com).