Having just celebrated National Farm Safety Week and 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.