Livestock producers should exercise caution when agitating pits under buildings whether they are partial pits or total building pits according to Dan Meyer, Iowa State University Extension Ag Engineer field specialist in Fayette. Hazard control and accident prevention are dependent upon the awareness, concern and prudence of personnel involved in the operation and use of pumping equipment in livestock facilities with stored manure under a slotted floor. A story came across my desk just recently about a man in Iowa who had been pumping from a partial pit and almost lost his life when he went in to check on why some pigs were squealing just after starting the agitation pump.
Hydrogen sulfide (H2S) is a dangerous gas when it exceeds over 100 ppm concentration level. The higher the concentration, the more deadly it is. High concentrations of 500 to 700 ppm can cause loss of unconsciousness and possible death. The gas concentration increases to its highest level usually twice during pit agitation. The first time is in the first thirty minutes of agitation and second when the tank is near empty and the recirculating pump discharge is above the liquid level.
There are several precautions that can be exercised to minimize dangers to livestock and people. The most important is to dilute the gas concentration by exchanging as much air as possible inside the building with outside air when pumping or agitating. The most effective exchange is by pulling air down through the slats and exhausting it out through pit fans. Make sure the curtains stay down during pumping. Disconnecting the curtain controller would ensure it doesn’t raise the curtain due to low building temperature. A one-foot opening for every ten feet of building width and a one mph wind exchanges the air once a minute which is a summer rate. Tunnel ventilation fans work just like a constant breeze through the building. Maintain at least two feet of freeboard in the pits with beams or one foot in partial slotted floor pits to allow air to move to pit fans. If storage time is a problem consider wet/dry feeders or the big cup waterers.
People should stay out of the livestock building when the pit is agitated. One individual on a pumping crew I visited with was knocked out just by looking over the curtain on the windward side during initial pump start-up. If pigs are having a problem, shut off the agitation pump and let the hydrogen sulfide clear the building with the fans or air movement through the curtains or both.
It is recommended that warning signs be posted above the chopper pump holes to remind pumpers of the toxic gases that can exceed safe levels. Utilize corrosion-resistant signs or stencil safety wordage such as “Danger Manure Storage” on the concrete wall above the chopper pump holes.
Some alternatives to worrying about gas concentrations are to consider buying hydrogen sulfide gas detection tubes or portable instantaneous-reading instruments (about $1000) to test the environment or store manure outside the building or utilize a pit additive. The instruments do have red blinking lights and alarms that can go off at preset levels of ideally 100 pm. Note, not all pit additives are equal on reducing hydrogen sulfide levels during agitation. Testing is still being done by universities as to their effectiveness. Unfortunately, the additive needs to be added three to four months before agitation so they have time to break down organic solids.
Dan Meyer/JLH
4/30/2006