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3.4.2 Explosive Atmospheres The potential for explosive atmospheres exists when the following conditions occur 1) the levels of combustible gases accumulate to within the explosive limit range; 2)the gas is generated in the presence of oxygen; and 3) there is a source of heat or ignition. Explosive conditions may be controlled by air monitoring for explosive gases during drilling operations. Air Monitoring can reduce risks by indicating when action levels have been exceeded. Inert gases (nitrogen) shall be used to displace combustible gases. Intrinsically safe equipment shall be used whenever possible. All operations shall cease if oxygen concentrations exceed 21.5 percent or if combustible gas measurements area are greater than 10% of the LEL for the gas of concern. 3.4.3 Heat Stress Heat stress may be a hazard for workers wearing protective clothing even if the temperature is moderate. The same protective clothing that shields the body from chemical exposure prevents heat and moisture from dissipating. Personal protective clothing can therefore create a hazardous condition. Depending on the ambient temperature and the work being performed, heat stress can occur very rapidly-within as little as 15 minutes. If an employee's pulse rate exceeds the maximum age adjusted heart rate (0.7(220-AGE)), and/or oral temperature exceeds 100.4 ❑ F, the employee shall be required to stop work and rest or move to an air-conditioned room. The affected employee may be allowed to return to work after his/her pulse rate has dropped below 100 beats per minute. Fluids shall be provided and rest breaks will be taken. The frequency of breaks will increase with the temperature. Such items as cooling vests, portable fans and breaks in air-conditioned areas shall be used if necessary. 3.4.4 Noise Noise is found at construction Sites in such operations as transportation and with heavy construction equipment. Noise has been defined as unwanted sounds. The human ear can tolerate a certain amount of sound without any harmful effects. The OSHA standard allows 90 dB (A) for a full 8 hours and for a lesser time when the levels exceed 90 dB (A). It is usually safe to assume that if you need to shout to be heard at arm's length, the noise level is at 90 dB (A) or above. Hearing protection will be utilized by personnel operating or working around construction equipment or power tools. Various actions can reduce noise when it reaches 90 decibels. High noise operations will be performed at times that expose the fewest workers. When these operations cannot be performed during off hours, engineering controls will be utilized to reduce sound level reading to below acceptable levels. This may be performed by using barriers to isolate the operations or modifying the tool itself(muffler on jack hammers). FREY Page 6