Health Hazard Assessment (HHA)

 Hazard Category - Oxygen Deficiency

Last Updated: July 19, 2021
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Oxygen Deficiency

Coordinate with the Health Hazard Assessment (HHA) Program early in the acquisition process in order to eliminate or control the potential for oxygen-deficient environments in materiel. Subject matter experts from the Industrial Hygiene Field Services Division provide input for HHAs related to oxygen deficiency. 

Under certain conditions, atmospheric oxygen concentrations may be reduced below those commonly found in air (20.9% by volume). Oxygen-deficient atmospheres are extremely dangerous. One breath of air at a low enough oxygen level immediately renders a person confused or unconscious, which likely necessitates a rescue. More often than not, rescuers entering the affected space without proper equipment and an understanding of the hazard may become quickly and severely impaired as well. 

General Ventilation

General ventilation of occupied spaces provides adequate outdoor (i.e., fresh) and recirculated air for breathing and the elimination of hazardous substances. It contributes not only to the comfort and efficiency of personnel but also to improved worker health because adequate ventilation helps to control odors, extreme temperature and humidity conditions,  carbon dioxide buildup, and the spread of communicable diseases via contamination of airborne dust and droplets.

Data Requirements
Provide data to assess general ventilation such as the total supply airflow rate, outdoor airflow rate (or air exchange rate), volume of the enclosure, and number of occupants. Collect air exchange rate data according to TOP 02-2-614A for vehicles and TOP 02-2-622 for tents and shelters1,2Provide use scenario information including the frequency and duration of time spent in the enclosure, tasks performed by system operators, window positions during operation, and environmental conditions. 

Health Protection Criteria
The ventilation requirements for manned spaces varies based on the system type, volume, and number of occupants. The most restrictive outdoor air requirement is approximately 20 cubic feet per minute per person (cfm/person)3. A manned space is a space occupied continuously for more than 20 minutes, but not a confined space3. The system intake should be located in an area where the concentration of exhaust and/or dust is minimal, including when a vehicle is moving. Note: MIL-STD-1472G is being used in the interim to assess ventilation while the new version H requirements are under review. 

Other Sources and Considerations

Certain systems, such as Army watercraft and tanker vehicles, may have confined spaces. Some confined spaces may require a permit for entry IAW 29 CFR 1910.46 and DA Pam 385-104,5. Dilution and local exhaust ventilation require specific testing and special assessment considerations. Some environments may be more likely to be oxygen-deficient, such as confined spaces, subterranean environments, and high altitudes. Exposure to asphyxiants may be considered additive to other exposures to oxygen-deficient environments. Oxygen supply during dive operations may also be assessed. 

For more information and guidelines for assessing oxygen deficiency, see Technical Guide 351D, Health Hazard Assessor's Guide: Chemical and Biological Health Hazards.


(1) ATEC. 2020. Test Operations Procedure (TOP) 02–2–614A, Toxic Hazards Testing for Military Vehicles. Aberdeen Proving Ground, Maryland.

(2) ATEC. 2020. TOP 02–2–622, Toxic Hazards Testing for Military Equipment and Materiel. Aberdeen Proving Ground, Maryland.

(3) DOD. 2012. Military Standard (MIL-STD) 1472G, Department of Defense Design Criteria Standard: Human Engineering. External Link

(4) OSHA. Title 29, Code of Federal Regulations (CFR), Part 1910.146, Permit-required confined spaces. External Link

(5) DA. 2010. Pamphlet 385-10, Army Safety Program. External Link