My name is Chinomso Ibe. I am a graduate research assistant at the University of Minnesota, and this is a hands-on activity
demonstration of how to select and don respirators.
I developed this activity along with Pete Raynor from the University of Minnesota
and with the help of students at Dakota County Technical College.
Part one of this activity entails the selection of suitable respirators for nanoparticles.
The selection of a respirator is determined by the Assigned Protection Factor, also known as APF, for a particular exposure.
The APF of a respirator is the level of protection a properly fitted respirator would be expected to provide a user.
For example, an APF of 10 for a respirator means that a user could expect to be protected
against a pollutant at a concentration 10 times the occupational exposure limit.
An APF is determined by calculating the hazard ratio of the exposure.
This is achieved by dividing the airborne contaminant concentration by the occupational exposure limit of the contaminant.
The selected respirator should have an APF equal or greater than the Hazard Ratio.
Learners will use the hazard ratio formula to select suitable respirators for 3 exposure scenarios in this activity.
In scenario 1, an occupational exposure limit, or OEL, established by the National Institute for Occupational Safety and Health,
also known as NIOSH, is referred to as a recommended exposure limit or REL.
The REL for ultrafine titanium dioxide exposures during a full time work shift per week is 0.3 milligram per cubic meter.
The measured air concentration of titanium dioxide in a room is 2.6 milligrams per cubic meter.
What APF is required for respiratory protection? What type of respirator is suitable to protect against this exposure?
To determine the hazard ratio for this exposure, divide the measured airborne particle
concentration for titanium dioxide by its OEL, in this case, the REL for titanium dioxide.
Thus, 2.6 milligrams per cubic meter divided by 0.3 milligram per cubic meter gives us a hazard ratio value of 8.7.
Learners should choose an APF equal or greater than 8.7. Therefore, the minimum APF for this exposure is 10.
Using the illustrations provided, a suitable respirator against the particulate exposure of
titanium dioxide is the filtering facepiece respirator.
In scenario 2, an OEL established by the American Conference of Governmental Industrial Hygienists, also known as ACGIH,
is referred to as a threshold limit value, or TLV.
In the production of silver selenide nanopowder in a laboratory, hydrogen selenide gas is used as a precursor.
The TLV for hydrogen selenide is 0.05 parts per million.
The concentration of hydrogen selenide in the laboratory room is measured at 0.34 parts per million.
What APF is required for respiratory protection? What type of respirator is suitable to protect against this exposure?
Similarly in this scenario, learners should divide the concentration for hydrogen selenide gas
in the room by the given TLV for hydrogen selenide.
Thus, the hazard ratio equals 0.34 parts per million divided by 0.05 parts per million and the answer is 6.8.
For a hazard ratio of 6.8, the minimum APF of 10 should be chosen.
A suitable respirator against this gas exposure is the half-mask elastomeric respirator with an appropriate cartridge for hydrogen selenide.
In scenario 3, the NIOSH REL for carbon nanotubes is 1 microgram per cubic meter for an 8-hour time-weighted average.
The measured air concentration of carbon nanotubes in a room is 0.23 milligram per cubic meter.
What APF is required for respiratory protection? What type of respirator is suitable to protect against this exposure?
First, learners should make appropriate conversion from micro grams per cubic meter to milligram per cubic meter.
So, 1 microgram per cubic meter equals 0.001 milligram per cubic meter.
Then, learners should proceed in dividing the measured airborne concentration for
carbon nanotubes by the given REL for carbon nanotubes.
Thus, the hazard ratio equals 0.23 milligram per cubic meter divided by 0.001 milligram per cubic meter, and the answer is 230.
For a hazard ratio of 230, the minimum APF is 1000.
A suitable respirator against this exposure is the full facepiece supplied air respirator with an auxiliary escape bottle.
In the second part of this activity, learners are asked to don and check the fit of a filtering facepiece respirator.
Learners will need a hand sanitizer, which can be bought at local grocery stores and
an N-95 disposable filtering facepiece respirator, which can be found online in various sizes.
An N95 respirator provides protection against particulates and will remove 95% of particles in the air that is breathed.
Learners should cleanse their hands with the hand sanitizer before handling a filtering facepiece respirator to reduce transfer of
contaminants to the face and the respirator.
Learners should pre-stretch around the entire length of the top and bottom straps before putting the respirator on the face.
Next, cup the respirator in the hand, with the nosepiece at the fingertips, allowing the straps to hang freely below the hand.
Place the respirator firmly over the nose, mouth, and under the chin.
Learners should ensure the respirator is situated on the face such that there is enough room for glasses or eye protection, if needed.
Take the bottom strap, stretching and positioning it around the neck and under the ears.
Also, stretch and position the top strap at the crown of the head.
Readjust the straps if they are overly twisted or if the straps are too tight.
Finally, using the fingers, learners should gently press the thin metal wire along the upper edge of the facepiece against the bridge of the nose.
To ascertain a good seal, learners should perform a positive pressure seal check by
covering the front of the respirator with both hands and exhale sharply.
Pressure should be built within the respirator without leakage around the edges.
If you feel air leakage around the nose, readjust the nose clip.
Additionally, if there is air leakage around the other edges of the respirator, readjust the position of the respirator and the straps.
Then, repeat the seal check.
To verify a respirator is correctly sealed, a fit test is conducted to assure the expected level of protection to a contaminant is provided.
During a fit test, wearers perform specific test exercises to simulate motions they may make while wearing a respirator.
While the following activity is not a formal fit test, performing some of the fit test exercises should give a sense of what a fit test entails.
The first exercise is the facing forward test. Learners should stand and breathe normal for 30 seconds without talking.
Repeat the seal check to check for air leakage.
The second exercise is the bending over test.
Learners should repeatedly bend at the waist as if trying to touch toes with fingers, for 30 seconds.
Repeat the seal check after the second exercise.
The third exercise is a talking exercise. Learners should recite the passage referred to as the “Rainbow Passage”.
Perform a seal check at the end of the third exercise.
When removing or doffing the respirator, learners should not touch the outer surface of the face piece.
Instead, slowly lift the bottom strap from around the neck and over your head. Then, lift the top strap and carefully remove the respirator.
Learners should perform hand hygiene after storage or disposal of the respirator.
I hope this video has helped you understand how to select and don a filtering facepiece respirator. Thank you for watching!
This lesson has been created by the Midwest Emerging Technologies Public Health and Safety Training Program,
also known as METPHAST, which is a collaboration between the University of Minnesota School of Public Health,
the University of Iowa College of Public Health, and Dakota County Technical College.
The content of this lesson is solely the responsibility of the developers and does not
necessarily represent the official views of the National Institutes of Health.