This is National Farm Safety and Health Week. In light of the recent deaths caused by manure gases in central Wisconsin, John Shutske, PhD of the University of Wisconsin-Madison has issued five things farmers should know about deadly manure gases.
1. Manure gases are formed during the breakdown of manure and other organic wastes
When manure is stored or sits for any period of time, it is broken down by bacteria. When in a pit, lagoon, basin, or other storage structure, the anaerobic bacteria that break down manure and other organic material produce different gases. The gases that are the biggest safety concern are hydrogen sulfide, methane, carbon dioxide, and ammonia. Gas production is a normal and natural process. The amounts of gases produced are dependent on animal species, temperature, amount of water in the manure, pH, length of storage time, and type of handling system. These gases are similar to carbon dioxide found in soda. When you agitate, pump, or move the manure in any way, it releases gas, similar to a can of soda being shaken.
2. Manure gases can be deadly
We know quite a bit about these four main gases found in stored manure. These gases are also found in other industrial settings including manufacturing and refining. Hydrogen sulfide (H2S) is especially deadly for people who work in close proximity to manure in a confined space or other area where there is no ventilation or air movement. The gas can build up to a highly toxic level quickly. Hydrogen sulfide is considered to be “immediately dangerous to life and health” when workers are exposed to levels of 100 parts per million (ppm) or more. The gas causes death at levels above 500 ppm. At levels of 1000 ppm or more, death can occur with a single breath. The gas paralyzes your diaphragm needed to inhale and exhale. This leads to rapid asphyxiation.
Methane is potentially an explosive gas. Both carbon dioxide and methane can also build up to high levels in enclosed areas, potentially causing death by displacing oxygen, leaving workers without the needed air to sustain life (at least 19.5% oxygen). Ammonia vapors are very irritating, even at low levels and can cause respiratory system and eye irritation or damage.
Ammonia has good “warning” properties. Most people find that working around ammonia is so unpleasant that they will quickly leave the area. Hydrogen sulfide has a strong rotten egg odor even at low levels of around 0.005 to 4 ppm. But, at higher levels, hydrogen sulfide affects the nerves that help you to smell things, and at high enough levels, you simply can no longer smell the highly toxic gas. Carbon dioxide and methane are both colorless and odorless, and without the correct safety monitor are impossible to detect.
3. Manure gases have killed many people in the past several decades
Since the early 1960s, nearly 150 people are known to have died in the U.S. because of manure-related gas incidents in confined spaces. We’ve seen two deaths in Wisconsin in the last month and a half. One was in a confined space (a liquid manure tanker) in Clark County and one was in a non-enclosed area in Portage County adjacent to manure being agitated within a football-field sized storage basin.
Of those manure-related fatality cases across the U.S. documented in recent reports over several decades, about one-half occurred on dairy operations. Almost 25% involved a young person under the age of 16. The most common activity (34%) at the time a person died was conducting repairs or maintenance activities on manure handling equipment followed by actions associated with trying to rescue another person entrapped or overcome in a manure storage space (22%).
4. Working around manure pits, basins, and other structures requires specific safety procedures and protocols
Because of the complexity and hazards found in working with manure handling and storage equipment, especially within confined spaces, we strongly recommend that repair, maintenance, fixing plugged systems, etc. be done from a safe location outside of the confined space. When that is NOT possible, the work must be done by persons with the right qualifications, technical training, and safety equipment to do the job safely.
Safe confined space entry where manure gases or oxygen deficiency is known to be present or has the potential to be present (all manure storage structures) requires:
· Continuous air monitoring and testing equipment (a calibrated four-gas electronic monitor is recommended).
· Ventilation fans, blowers, ducting, etc. to dilute or remove toxic gases and increase oxygen levels to a measured safe level.
· Personal “retrieval” equipment (harness, cables, winch systems, etc.).
· Respiratory protection equipment (a supplied-air respirator is required such as a self-contained breathing apparatus for oxygen levels below 19.5% or gas levels above those which are “immediately dangerous to life and health” or IDLH. The IDLH level for hydrogen sulfide is 100 ppm).
In an outdoor, non-enclosed situation, based on the recent event in Amherst, Wisconsin (Portage County) we know that the potential for high risk situations exist even though this was not a confined space. It is imperative that any pumping/agitation work in the proximity of a manure storage facility occur with some wind present. At this time, we do not have enough information to provide a specific recommendation on minimum wind speed for those working adjacent (within 0 to 50 feet) to a non-enclosed structure such as this basin during agitation and pumping. This value is likely dependent on temperature, wind direction, humidity, presence of other nearby structures/obstructions, and other conditions. But it is clear that risk increases as wind speed decreases. To reduce risk in a non-enclosed situation, we are studying the use of a less expensive hydrogen sulfide monitor (a single gas detector with an alarm) which reduces the cost of equipment to 1/4th the cost of a four-gas unit. The webinar cited in the next section provides further information on H2S detection equipment.
5. Many resources exist to prevent manure-related fatalities and other events
Since farm safety and health specialists have been dealing with manure-related gases for many years, numerous resources exist and should be considered as farmers, nutrient/manure applicators, pumpers, haulers, etc. develop procedures and protocols for working around/near these potentially hazardous environments.
Source: Wisconsin Ag Connection
