Types of Masks and Face Coverings for the Community

These masks and face coverings provide varying levels of protection to the person wearing them and reduces exposure to others. Face coverings that are more than one layer, tightly woven, and are tight fitting to the face work better than single layer cloth or face coverings that are loose. The information below can be used to help people make decisions about protections levels with the resources that are available.

Fit Factor Definition: A fit factor of two reduces the exposure to small particles to ½ (50%). A fit factor of 20 reduces exposure to 1/20th (95%). A fit factor of one hundred the exposure down to 1/100th (99%). Even the lower performing face coverings reduce exposure somewhat. If you want to reduce it more here are your options. 

Type of mask/
respirator/face cover

Fit factor range 
1 is nothing 100 is fitted N-95



Face shield alone 1.0 to 1.5 Provides very little protection against anything except droplets. A face shield combined with a surgical mask has been effective at limiting spread.
Bandana (single layer cloth, single layer gaiter) 1.5 to 3 Single layer cloth face coverings offer very little protection. Doubling up the layers and having them tight fitting improves coverage.
Multiple cloth layer and multiple layer gaiter tight fit 3 to 15 Tight weave cloth with multiple layers of sometimes different fabrics or an inserted filter improves the filtration. The key is having a good nose clip and a tight seal around the face without air gaps. 
Surgical mask – ear loops only 3 to 10 These tend to gap at the cheeks and the nose, clip must be adjusted. Combining an interior surgical mask with an external cloth will improve fit.
Surgical mask with ear savers 6 to 20 The ear savers help pull the surgical mask closer to the cheeks. Need to bring a spare surgical mask as the ear savers can cause the ear loops to break. 
Surgical mask covered with double layer cloth face covering  15 - 25 The double layer of cloth face coverings helps to hold the surgical mask close to the face. Make sure the additional layers do not make it too difficult to breathe. 
M3 - U of M mask 5 to 100 Filter material from Cummings designed to remove small particles. Fit is variable and construction needs to be precise for optimum fit.
KN-95 KF-94 3 to 30

Quality varies. Fit factor varies with nose shape and the quality of the nose clip. Broader nose shapes usually have higher fit factors.

Check for counterfeit respirators.

There may be some irritation with the back of the ears as most of these respirators are ear loops. Ear savers can help. 
M4 – U of M mask under development 20 to 140 Fit factor varies with nose shape. Broader nose shapes usually have higher fit factors. Upgraded design over the M3 using the same Cummings material and including an inner foam lining to improve fit. 
Power filtered respirators (nano PAPRs)  20 to 200

A surgical mask or KN-95 mask has a hole cut in it and a filtered air supply is attached.  

Different methods are used for hose attachment. Some are more secure than others. 

There is currently variability in the filtration efficiency of the powered filter devices. Some as low as 20 others as high as 10,000. 

Battery life on maximum airflow is 3 to 4 hours.

Power filtered respirators (nano PAPRs) combined with a Badger + tight face cover. 20 to 200

Two air filtering devices are attached to the underside of the badger + face covering.  

Different methods are used for hose attachment. Some are more secure than others. 

There is currently variability in the filtration efficiency of the powered filter devices. Some as low as 20 others as high as 10,000.  

Battery life on maximum airflow is 3 to 4 hours.

Many hybrid designs with insertable filters 2 - 30

Highly variable performance. 

In most cases a well-fitting KN-95 would work better. 

Health care respirators - This type of personal protection should have priority for health care workers who must interact closely with patients who are or likely infected with COVID-19 and for people who must enter the spaces where patients with COVID-19 are housed or people researching infectious agents.    

N – 95 filtering face piece 100+

Need to have fit test for optimum performance. Check FDA for list of counterfeit respirators.

The N-95 respirators work best if the face is clean shaven in areas where the respirator contacts the skin.

P-100 filtering face piece 100 to 200+

Thicker respirator usually with exhalation valve for lead paint abatement. The exhalation valve must be covered for community protection.

Thick material makes it more difficult to breath. It can get hot. 

Elastomeric mask with HEPA filter and filtered exhaust 200 to 5,000+

Most have P-100 cartridges and exhalation valves that need to be covered. Newer ones do not have an exhalation valve.

More recent models have filtered exhalation valves. The masks can be washed. If the filters have  a plastic cover, they can be reused.

PAPR with HEPA filter 200 to 1000+ Positive pressure HEPA filter respirator. Need daily cleaning. Hoods need to be replaced when worn out. Batteries need charging. Units can wear out.  Higher up-front cost.

Reference: CDC - https://www.cdc.gov/mmwr/volumes/70/wr/mm7007e1.htm Maximizing fit with surgical mask and cloth face coverings.