Training and preparation are keys to avoiding a tragic manure pit incident, according to Chuck Schwartau, University of Minnesota regional Extension educator.
“The emergency response process should be second nature to anyone working at an agricultural site,” he says. “All staff working around a confinement site should be receiving regular reminders about the hazards and warning signs that something might be wrong. Everyone needs to be ready to take action in an emergency and it is crucial that everyone working in the area knows where to find the safety equipment and how to use it.”
Schwartau says safety equipment should be conveniently located near the spot where it might be needed. This equipment could include safety harnesses, poles and ropes, in the case of manure pits, and rowboats located near manure lagoons.
All manure pits should be ventilated. “Just because a barn is empty does not mean the fans should be turned off. If people are going to be working in the barns, ventilation should be provided and air should be moving through that barn,” Schwartau says. If the space between the bottom of the slats and the manure surface is less than 1 ft., it is best to draw down the liquid manure before the pit is agitated.
During pit agitation and pumping, gas detection devices with extension tubes should be used to test the safety of the environment before humans enter the building. “Employees should also be aware that concentrations of dangerous gases can be very different within different parts of the building. There are pockets of good air and pockets of ‘dead’ air, so it is very important to test carefully,” he stresses.
Signs should be posted on the door of a building where the manure pit is being pumped or agitated. It is important that signs be multilingual to reflect the languages of the workforce as well. “Treat all manure pits as confined spaces and post hazard warnings and signs, in addition to erecting fencing, around all outside manure-holding structures,” Schwartau suggests.
If it becomes necessary for a person to enter the manure pit, the person should be wearing a safety harness with an attached rope. A second person should be standing by outside of the pit, ready to pull a potential victim out if necessary.
Schwartau says the four primary gases of concern are hydrogen sulfide, methane, carbon dioxide and ammonia. These gases become dangerous because they displace oxygen.
The minimum oxygen level for safe entry into a building is 19.5%, he notes. If gases displace oxygen, a human will have impaired judgment and difficulty breathing when oxygen levels hit 16%. When oxygen levels dip to 14%, faulty judgment and rapid fatigue set in. At oxygen levels of 6% or lower, death can occur in minutes.
Methane is lighter than air and normally occurs near the top of the manure pit. Methane can displace enough oxygen to cause death by suffocation. This odorless gas is flammable at concentrations ranging from 5-15%, and reaches potentially explosive levels at 50,000 to 150,000 ppm. “Make sure all employees are aware that there should be no smoking around manure pits too due to the explosive potential,” Schwartau states.
Hydrogen sulfide is a highly toxic gas that has a “rotten egg” odor at low concentrations, but can paralyze the sense of smell at higher concentrations. At 20 ppm of hydrogen sulfide, exposure for more than 20 minutes can cause eye, nose and throat irritation. At 50-100 ppm, humans experience vomiting. When levels reach 200 ppm, dizziness, nervous system depression and fluid build-up in the lungs takes place. “If you start to notice any of these symptoms, that should be the key indication that you should get out of the situation,” he warns. At levels beyond 200 ppm, death can occur.
Carbon dioxide is odorless and frequently occurs at the bottom of the manure pit because it is heavier than air. Carbon dioxide exposure causes headache, drowsiness and labored breathing. Humans should not exceed a maximum exposure of 1,500 ppm, according to Schwartau.
Ammonia has a sharp odor and severely irritates a person’s eyes, nose, throat and lungs. Exposure to high concentrations can be fatal.
To prevent manure pit and pumping accidents, Schwartau emphasizes the importance of advance planning. “Do everything you can to get serviceable parts of equipment accessible from outside the barn to help reduce the need to go into manure pits,” he says. “Most importantly, make sure employees train and retrain when it comes to safety procedures.”