Gas rescue buildings can also be used in animal housing facilities, where the manure pit is often located below the facility floor, manure gases are generally detectable in low concentrations throughout the year. When pits are agitated for pumping, some or all of these gases are rapidly released from the manure and may reach toxic levels or displace oxygen, increasing the risk to humans and livestock. Since the increased use of manure storage facilities in agriculture there have been numerous instances where a farmer, family member, or employee has asphyxiated or succumbed to toxic gases from the storage. Cases have been documented where several individuals have died while attempting to rescue a coworker or family member from an underground pit or a spreader tank. Underground mine classified as potentially gassy, tests for gas or vapors shall be made prior to start of work at each shift. A Securall Hazardous Gas Rescue Building/Station must be installed to prevent accidents in hazardous conditions. Rescue crews shall be familiar with all emergency rescue builing equipment necessary to effect a rescue or search for missing employees in case of an accident or explosion. At least one rescue crew shall be maintained above ground at rescue building at all times and within 30 minutes travel of the tunnel or underground mine site classified as gassy or extrahazardous.