particular atmospheric contaminant, refer to table 6-1. NOTE: When labels only are colored, the cart- ridge or canister will either be gray or a natural metallic color. The National Institute for Occupa- tional Safety and Health (NIOSH) must approve all  cartridges. The color-coded label also specifies the max- imum contaminant concentration level against which the cartridge or canister provides protec- tion. For example, a label may read as follows: DO NOT WEAR IN ATMOSPHERES IMMEDIATELY  DANGEROUS  TO LIFE. MUST BE USED IN AREAS CONTAINING AT LEAST 20% OXY- GEN. DO NOT WEAR IN ATMO- SPHERES CONTAINING MORE THAN 1/10% ORGANIC VAPORS BY VOL- UME. REFER TO COMPLETE LABEL ON RESPIRATOR OR CARTRIDGE CONTAINER FOR ASSEMBLY, MAIN- TENANCE, AND USE. NOTE: The 20% oxygen requirement cited above does not apply to submarines, which may operate with an atmosphere of as low as 18.5% oxygen. Education is vital to the overall success of a hearing conservation program. Make sure your personnel receive instruction in and understand the rationale for the following elements of the hearing conservation program: 1. 2. Proper wearing and maintenance of hearing-protective devices The command program and personnel responsibilities for off-duty practices to help protect hearing Encourage your personnel to use hearing- protective devices during off-duty activities when they are exposed to hazardous noise sources, such as lawn mowers, chain saws, and firearms. All personnel exposed to gunfire in a training situa- tion or to artillery or missile firing under any cir- cumstances must wear hearing-protective devices. If your personnel must work in hazardous noise areas or with equipment that produces sound levels greater than 84 dB or peak sound pressure levels of 140 dB, enter them in a hear- ing testing program.   Personnel should have received a reference hearing test upon entry into naval service. Do not assign personnel who do not have a reference hearing test in their health record to duty in designated hazardous noise areas until they receive a reference hearing test. All person- nel should receive a hearing test periodically and before termination of naval service. HEARING CONSERVATION AND NOISE ABATEMENT HEAT STRESS Hearing loss is recognized as an occupational hazard related to certain trades. For example, gunfire and rocket fire produce high-intensity im- pulse or blast noises, which can cause hearing loss. Hearing loss can also result from the continuous or intermittent noises of aircraft and marine engines and industrial activities. Hearing loss has been and continues to be a serious concern. Therefore, the Navy has developed a hearing con- servation program to prevent occupational noise- related hearing loss. The program requires the following preventive measures: 1. 2. The survey of work environments to iden- tify potentially hazardous noise levels and to identify personnel at risk The modification of environments that contain, or equipment that produces, potentially hazardous noise to reduce the noise level to acceptable levels whenever technologically and economically feasible Heat stress is the strain placed on the body as it attempts to regulate its temperature as a result of any combination of air temperature, thermal radiation, humidity, air flow, and work load. This condition can readily produce fatigue, severe headache, nausea, and poor physical and mental performance. Prolonged exposure will cause heat exhaustion or heat stroke and severe impairment of the body’s temperature-regulating ability. If not properly treated, these conditions can be life threatening. Adhere to the command’s Heat Stress Pro- gram by reporting heat stress conditions as they occur. Educate your division about the Heat Stress Program, the identification of heat stress conditions, stay time, and rotation of personnel. Heat stress has occurred in engineering spaces, laundries, sculleries, steam catapult spaces, and workshops aboard our ships. In many instances, clogged ventilation systems, damaged or missing 6-12