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® HEALTH AND SAFETY SECTION A. PURPOSE AND GENERAL INTRODUCTION ® The purpose of this section is to provide information on health and safety practices for use in working with landfill gas (LFG) at municipal solid waste (MSW) landfills. ® This document is based ona consensus of practices developed based on specific ® experience with LFG. This document is not intended to apply to hazardous waste ® sites, however certain special circumstances which may be encountered at MSW landfills are addressed. The Occupational Safety and Health Act (OSHA) of 1970 requires employers to furnish a place of employment which is free of recognized hazards that-cause or are ® likely to cause death or serious.`physical harm to employees. Employers have the obligation to eliminate recognized hazards, to comply with safety and health standards, and to provide the necessary information and training to the employee. ® Landfill safety requires more than the common sense safety procedures common to ® all industries. Bacterial decomposition of trash results in the formation of methane, ® a colorless, odorless, potentially explosive gas that together with other volatile ® materials is emitted into the atmosphere and migrates through the soil into surrounding areas. Air quality studies consistently show that concentrations of most ® potentially hazardous substances in the ambient air on and in the vicinity of solid ® waste landfills are well below threshold limits. Threshold limits are those limits above ® which chemical substances may cause harm. Various standards for threshold limits ® are discussed later in this text. However, in the presence of confined or enclosed areas and venting sources of gas on or adjacent to landfills, dangerous concentrations ® of combustible and possibly toxic gases may accumulate. LFG is chiefly composed ® of four common gases: methane, carbon dioxide, nitrogen and oxygen. The first ® three are simple asphyxiants; hence, oxygen depletion may also occur in these areas ® of confinement. Therefore, safety procedures should be followed at all times (e.g., ® monitoring for adequate levels of oxygen and for explosivity in vaults or excavations, etc.). When conducting certain special activities such as drilling and trenching in refuse, or entering confined spaces such as vaults and excavations, toxic and odorous gases can ® be present. Odorous gases cause nausea in some persons. Toxic gases may also be present at concentrations above or below the levels deemed safe for human ® exposure-, there is always a potential for levels to be sufficient to cause permanent ® and irreversible damage and even death. Monitoring of site conditions during these ® special activities is therefore recommended even where not specifically required by law. ® I: 1