COVID-19: Moving Forward - Ventilation, Face Coverings, and Room Air Purifiers


Normal maintenance to ensure proper operation of campus building ventilation systems has continued through the summer and into Fall 2021.

  • Outdoor air supplies for ventilation systems are checked for proper operation while still maintaining indoor air quality, temperature and humidity
  • Ventilation systems are run before and after normal operating hours to flush the air in the buildings
  • Conditioned air is filtered at the recommended level (known as “MERV 13” or better) before being distributed by the system to individual rooms.

Other than a few unique applications, HEPA filters are rarely used in building HVAC systems, and could not be installed in our buildings without major system modifications.  In addition, the current information from the Centers for Disease Control and Prevention states:

“While airflows within a particular space may help spread disease among people in that space, there is no definitive evidence to date that viable virus has been transmitted through an HVAC system to result in disease transmission to people in other spaces served by the same system.”


N95 Respirators

OSHA considers disposable, filtering face-pieces (N95, dust masks) to be respirators and their use is regulated. Employees whose job description requires them to wear respiratory protection must participate in the ISU Respiratory Protection Program. Refer to the ISU Respiratory Protection manual for program details.

Employees who voluntarily use these respirators for purposes that are not part of job requirements do not need to participate in the ISU Respiratory Protection Program. Voluntary users must follow the use, storage, and disposal guidelines contained on the "Information for Disposable Respirator Users" web page.

Information for Disposable Respirator Users | Environmental Health and Safety | Iowa State University (


KN95 & KF94 masks

EH&S considers the use of masks with designations such as KN95 or KF94 to fall into the category of face coverings (cloth, disposable surgical masks, gators) versus respirators.  EH&S recommends caution related to KN95 and KF94 use as they do not meet NIOSH performance standards and must NOT be used as protection from workplace hazards.

The link below provides information to consider when selecting face coverings. For those departments that wish to provide more protective face coverings for their employees, EH&S recommends the purchase of disposable 3-ply masks and/or 3M model 8200, N95 respirators available at Central Stores.

Face Coverings vs. Respirators


Room Air Purifiers

Current literature is mixed on the effectiveness of room air purifiers. Much of this depends on design, placement, filter efficiency and user maintenance.  A primary consideration is the efficiency rating of the filtration system. The higher the filter efficiency rating, the more efficient the particle filtration achieved. Keep in mind that as filter efficiency increases, a proportionate increase in cost will occur. Cost for these units can range from 100s to 1000s of dollars. Another important, but often overlooked, consideration is user performed maintenance. Routine maintenance (i.e., cleaning and filter replacement) is critical to ensure effectiveness of the device.

In general, EH&S does not advocate the use of these nor are we prepared to recommend specific brands or models. If it is decided to proceed with a purchase of these devices, below are a few guidelines that should be considered when selecting an air purifier.

1) The efficiency rating of the unit's filtration system should be a primary consideration (systems with higher ratings should be prioritized)

2) Do not purchase any product that generates ozone to eliminate odors. Ozone is damaging to the respiratory system and therefore is unsuitable for use in the office environment.  

3) If odors are of concern, select equipment that uses a filter system that contains a charcoal layer or a separate charcoal pre-filter.

4) The unit must be properly maintained per the manufacturer's recommendations – see cleaning and filter replacement

5) To aid with maintenance, look for a unit with an end of filter service life indicator

6) The unit should be sized to match the volume or square footage of the space it will be placed in

7) Select from units that are UL listed and labeled

8) Due of their electrical power requirements, these devices must be plugged directly into an outlet (use of extension cords or temporary power strips should be avoided).

Updated Tuesday, August 24, 2021