OXYGEN DEFICIENCY

Data Requirements and Initial Recommendations.
(1) Provide ventilation test data (e.g. maximum personnel, area volume, total fresh and recirculated airflow rates) collected in accordance with Test Operating Procedure (TOP) 1-2-610 (reference 1) to this Command for completion of a comprehensive HHA.   

(2) Ensure the design and operation of vehicle cabs, shelter ventilation systems or environmental control units provide the required rate of fresh and recirculated air to occupants during all operational scenarios in accordance with Military Standard (MIL-STD)-1472G paragraphs 5.5.2.1.3 (reference 2).    

(3) Ensure the design of maintenance-type shelters includes general ventilation and local exhaust ventilation (LEV) as described in MIL-STD-1472G (reference 1) to capture and eliminate airborne health hazards generated during maintenance activities.     

(4) Refer to the Occupational Safety and Health Administration’s (OSHA) definitions of “confined space” or “permit-required confined space” for additional guidance on ventilation requirements (reference 3).  A confined space has limited means for entry or exit, and is not designated for continuous occupancy.  A permit-required confined space has one or more of the following characteristics: contains or has the potential to contain a hazardous atmosphere, contains a material that has the potential to engulf an entrant, has walls that converge inward or floors that slope downward and taper into a smaller area which could trap or asphyxiate an entrant, or contains any other recognized safety or health hazard (e.g. unguarded machinery, exposed live wires or heat stress).

Health Effects.
General ventilation of occupied spaces provides fresh and recirculated air for adequate breathing air and the elimination of toxic chemicals.  It also contributes to the comfort and efficiency of personnel and improved worker health since 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.  In general, dust may cause temporary effects such as eye/respiratory irritation, coughing, and possible aggravation of existing conditions of asthma.

Medical Criteria.
(1) The MIL-STD-1472G paragraph 5.7.9.4.1 (reference 2) recommends personnel not be exposed to the concentrations of toxic substances in excess of the limits specified in either the Department of Defense Occupational Safety and Health standards or specialized standards applicable to military unique equipment, systems, or operations.

(2) The most restrictive fresh air requirement for mobile enclosures, shelters, or buttoned up vehicle cabs contained in MIL-STD-1472G, Figure 34, is approximately 20 cubic feet per minute per person (cfm/person) (reference 2).  As the enclosure or shelter volume per occupant increases, the outdoor/fresh air requirement decreases.  Figure 34 also contains the outdoor/fresh and recirculated air required for variations in shelter volume/number of occupants.  Outside fresh air should be provided at a minimum rate of 20 cfm/person for traditional vehicle cabs.  The air velocity at each vehicle occupant’s head location should be adjustable either continuously or with not less than three settings (i.e. off, low, high) from near zero to at least 400 feet per minute (reference 2).

MIL-STD-1472G, Figure 34.  Minimum Ventilation Requirements


Image Source:  MIL-STD-1472G, Department of Defense Design Criteria Standard - Human Engineering, 11 Jan 12

(3) The MIL-STD-1472G, paragraph 5.7.11 states that the ventilation system intake shall be located in an area where concentration of dust is minimal, including when a vehicle is moving.  Filters shall be capable of removing dust particles above five microns in diameter.  Dust skirts, which are of great value in reducing the dust raised around a vehicle, shall be provided.

(4) Biologically inert, insoluble, or poorly soluble particles, for which little data exists, may have adverse effects and the American Conference of Government Industrial Hygienist (ACGIH) recommends that airborne concentrations should be kept below 3 mg/m³ for respirable particles, and 10 mg/m³ for inhalable particles until such time as a TLV is set for a particular substance (reference 4).

References.
(1) Test Operations Procedure (TOP) 1-2-610, Human Factors Engineering Part I Test Procedures, 15 May 90. 

(2) Military Standard (MIL-STD) 1472G, Department of Defense Design Criteria Standard - Human Engineering, 11 Jan 12.

(3) Safety and Health Topics: Confined Spaces, 10 Jan 08, Occupational Safety and Health Administration (http://www.osha.gov/SLTC/confinedspaces/index.html).

(4) American Conference of Government Industrial Hygienist (ACGIH), 2012 Threshold Limit Values for Chemical Substances and Physical Agents and Biological Exposure Indices, ACGIH, Cincinnati, OH, 2012.