UNIVERSITY PARK, Pa. -- An incident in Virginia this month in which five people died after being overcome by noxious gases in a manure pit serves as a grim reminder of the need for caution when working around manure-storage facilities, according to a farm-safety specialist in Penn State's College of Agricultural Sciences.

"As manure decomposes or ferments, it produces gases that accumulate and reduce the amount of oxygen present," says Dennis Murphy, distinguished professor of agricultural safety and health. "These gases can be so concentrated that they can suffocate a person instantly, so it's imperative that people working around manure pits or other storage areas take proper precautions to avoid asphyxiation."

Manure produced on livestock farms often is stored until conditions are suitable for spreading it as fertilizer on crop fields. Under normal conditions, ventilating fans and natural air movement can minimize the build-up of harmful gases. However, when manure is being transferred between storage facilities or is being agitated or pumped in preparation for spreading, the hazard can be severe, especially in connection with covered, below-ground storage areas.

Hydrogen sulfide is the most dangerous manure gas, Murphy explains. Colorless and heavier than air, hydrogen sulfide may increase a thousandfold during agitation or emptying of manure.

"By causing respiratory paralysis, hydrogen sulfide can be fatal within seconds at high concentrations," he warns. "Although it has a rotten-egg odor at low levels, the human sense of smell is deadened at less-than-lethal levels. In addition, the odor may be masked by other smells common to livestock facilities."

Other hazardous gases -- such as carbon dioxide, ammonia and methane -- also can accumulate, displacing oxygen and potentially causing asphyxiation. In addition, methane is highly flammable and can cause explosions in the presence of a flame or spark.

Tragically, incidents related to manure gas often involve multiple fatalities. "When someone entering a manure storage facility is overcome by gases, the first reaction of nearby family members or farm employees often is to go in and help, and the would-be rescuers can quickly become victims as well," Murphy says.

Fatalities have occurred when farmers have entered manure-storage facilities to unclog a pipe or check on a pump. Murphy recommends that farmers not enter a manure pit for any reason. "The only safe way to enter a manure pit is by wearing a self-contained breathing apparatus, as well as a safety harness attached to a lifeline and mechanical lift so that a coworker can pull you out in the event of an emergency," he says.

Murphy offers the following recommendations for avoiding and responding to emergencies related to manure gases:

--Keep people and animals out of confinement buildings during manure storage agitation and pumping.

--Ventilate the area before and for several hours after pumping activities.

--Equip ventilation systems with alarms to warn of failure, and provide a back-up ventilation system and emergency power source in the event of a power outage.

--Allow one or two feet of air space above the manure to accommodate toxic gases.

--Keep manure agitators below the surface of liquid manure to reduce the amount of gas released.

--Eliminate or prohibit smoking, open flames or sparks near manure-storage areas.

--Use gas traps for emptying pipelines and for keeping gas from back-flowing into buildings.

--Warn visitors and guests and post warning signs about manure-storage hazards.

--If someone is overcome by manure gases, don't go in after them. Call 9-1-1 immediately, cease agitation and pumping activities, and ventilate the area.

For a free fact sheet about manure gases and manure-storage safety, contact the Penn State Cooperative Extension office in your county, or visit the Web at http://server.age.psu.edu/extension/factsheets/e/E28.pdf.

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EDITORS: Dennis Murphy can be reached at 814-865-7157 or by e-mail at djm13@psu.edu.

Chuck Gill 814-863-2713 cdg5@psu.edu