Understanding Respirator Selection: Full Face, Half Mask, or Hood Respirator

What's the difference in protection between a full face or half mask respirator? What about a tyvek hood respirator that is available with some airline systems? Which of these is best suited for a particular application or hazard? Do some offer more protection than others?

There are four steps involved with answering these questions. We'll try to make them easy to understand and follow. Ultimately, what you need to know is something called APF - Assigned Protection Factor. You'll see that the main difference between the various respirator types is their APF. The APF is designated by OSHA.

Choosing the Correct Respirator

Step 1: Identify the hazard for which you need protection. The SDS sheet will be helpful here. Generally, you will be dealing with either particulates (like asbestos, lead, fiberglass, or other toxic dusts and fibers) or fumes and vapors (like solvents or chlorine). You could even have all of these together.

Step 2: Identify the level of hazard present. This is easier said than done. Again, the SDS might be helpful here. You also might find help from others who have worked in similar applications or the manufacture of the product. Both may have some helpful data about hazard levels.

Once you know the hazard level present you'll need to compare it to OSHA's OEL (occupational exposure limit) or PEL (permissible exposure limit) for that hazard. This can usually be found with a Google search or in the NIOSH chemical guide. If you need help with this, give us a call.

If your level is lower than OSHA's OEL or PEL, you will not need respiratory protection. If it is higher, you will need respiratory protection.

Step 3: Now you need to identify the APF needed for the level of hazard present. The APF is the Assigned Protection Factor. It is discussed in detail in the OSHA 1910.134 Respiratory Protection Standard.

The APF is the key to understanding which type of respirator to use: half mask, full face, a tyvek hood, airline system, etc.

The way to determine the APF required in your application is to do this calculation: Exposure Level ÷ OEL or PEL = APF required.

For example, if it has been determined that the Exposure Level of the hazard (step 2) is 500 ppm and the OEL or PEL for that hazard as set by OSHA/NIOSH is 50 ppm (found in the NIOSH chemical guide), you will need respiratory protection that offers at least an APF of 10 (500 ÷ 50).

We realize that step 3 hinges on having access to the exposure level of your particular hazard. We recognize this may be hard for many companies to figure out. The SDS or the manufacturer of the hazard might be helpful here.

Step 4: This is the easy part. Now all you need to do is consult OSHA's APF chart (we've posted it below) and pick the respirator that meets or exceeds your requirement. If based on your calculations you need a respirator with an APF of 10, you can consult the OSHA chart and see that an air-purifying half mask respirator with the appropriate filter based on the hazard type from Step 1 will do the job. If you need an APF of 50, a full face respirator will be necessary.

OSHA APF Chart

Loose-Fitting Facepiece

You will notice on the APF chart something called a "loose-fitting facepiece." This is referring to the tyvek hood respirator that is available on our Allegro supplied air continuous flow systems. You should note that it offers a fraction of the protection of a full face respirator - an APF of 25 verses 1,000. So though the hood is convenient for those with beards, it may not offer enough protection.

NIOSH Chemical Guide Handbook

We highly recommend that you track down a NIOSH hazard guide handbook. Below is a sample picture. It provides you with the needed PEL/OEL levels that you need to make the correct respirator selection. It also gives respirator recommendations based on the OSHA APF chart. However, it is still necessary to know the exposure level of the hazard you are working with.

NIOSH Handbook



Posted by Corby Amos on

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About the Author

Corby has over 25 years of experience in the safety industry. His area of specialization is confined space, gas detection, and fall protection equipment and applications. He's advised hundreds of contractors, cities, manufacturing plants, and government agencies on what equipment best suits their applications.


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