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Warding Off Pit Foam Explosions

With manure deep pits filling in August and September in the Upper Midwest comes heightened safety concerns for area swine farmers, warn University of Minnesota agricultural engineers Chuck Clanton and Larry Jacobson.  

That’s because since 2009, at least 20 Minnesota swine barns have experienced flash fires or barn explosions as a result of manure deep-pit foaming. A producer survey conducted by the University of Minnesota Bioproducts and Biosystems Engineering Department determined that about 25% of the finishing barns in the Upper Midwest have identified foam in their manure pits and thus the potential for explosions or flash fires.

Human and animal safety are paramount, as is protecting buildings and their contents. To prevent fires and explosions, producers should follow several recommendations. Most importantly, producers should monitor at least weekly and determine the depth of foam, if any, in their manure pits.   

Take action if foam depth is above 6 in. and within 24 in. of the underside of the slotted floor. Actions could include:

  • Using a pit additive such as Rumensin­­ to reduce foam depth.
  • Removing some of the manure to allow additional capacity and headspace above the surface.


Be sure to properly ventilate your barn, based on outside temperatures along with animal age and size, to maintain acceptable air quality and keep methane concentrations below the explosive level.

Never turn off the barn’s ventilation system, even if there are no pigs in the building. If the barn is unoccupied, the minimum ventilation rate used for finishing pigs should be used to prevent methane buildup. The constant running of minimum ventilation rate should be 5 to 10 cubic feet per minute (CFM) per pig space (varies with age and size of pigs). Review references or handbooks with detailed information on ventilation management in swine facilities based on animal age and size (MWPS-32 Mechanical Ventilation Systems for Livestock Housing, 1990 or MWPS-33  Natural Ventilation Systems for Livestock Housing, 1989).

Use emergency backup electrical generation in case of main power failure.

Eliminate any source of sparking or flames, including:

  • Cigarettes, cigars, pipes, etc.
  • Sparking switches or motors.
  • Sparking or pilot light on water and/or space heaters.
  • Welding and/or grinding during repair of gates, feeders, waterers and similar objects.


Additional recommendations include:

  • Maintain a minimum of 12 in. of space between the top of the manure or foam and lowest concrete beam for adequate pit fan ventilation airflow.
  • Remove pigs from barn, if possible, when agitating and/or pumping manure. If not, use the maximum ventilation rate (roughly 10 times greater than the minimum rate) for an all mechanically ventilated system. For naturally ventilated buildings, curtains should be fully open with a breeze (minimum of 10 mph). Never enter a building during manure pit pumping.
  • Allow no liquid to leave the manure pit surface (rooster tailing) during agitation.


To learn more about manure management and air quality, visit

Clanton is a professor in the College of Food, Agricultural and Natural Resource Sciences. Jacobson is an engineer with University of Minnesota Extension.




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