Deadly Manure Gas Does Not Discriminate – Fight Manure Pit Hydrogen Sulfide
By: Stephanie Leonard, University of Iowa Industrial Hygienist Occupational Safety Manager
If storing, hauling, or applying liquid manure is part of your work, protecting personnel and livestock should be on your mind right now. Careful planning can make the difference between a safe outcome and lives lost; when maure pit hydrogen sulfide is present, it does not discriminate.
What is hydrogen sulfide?
The hazard is hydrogen sulfide (H2S) is a heavy, colorless gas with no warning properties at unsafe concentrations. It is lethal and unpredictable. H2S is one of many gases produced by bacteria that break down manure and organic matter, along with methane (a flammable gas), ammonia, carbon dioxide and others.
Hydrogen sulfide is emitted from manure and remains dissolved in undisturbed slurry; concentration in the surrounding air can vary from undetectable (0 ppm) to a few parts per million (ppm). At this low concentration, (3 ppm) H2S has a recognizable rotten-egg odor.
When manure is disturbed or transferred, H2S bubbles break through the surface into the air. (It’s like what happens when you shake a bottle of your favorite carbonated beverage before you open it.) During agitation and pumping, the gas is released in bursts. In a matter of seconds, manure pit hydrogen sulfide concentrations can increase a hundred to a thousand-fold.
Concentrations over 5 ppm cause increasingly severe health symptoms and outcomes; headaches, eye irritation, disorientation, collapse, loss of consciousness, and death. At 100 ppm, the concentration deemed Immediately Dangerous to Life and Health (IDLH), H2S is no longer detectable by sense of smell. If people or livestock are in the immediate environment with concentrations of 500-2000 ppm, the consequences can be fatal. These levels have been documented during agitation and pumping.
Fatal Scenarios
Over the last 40 years, many H2S related human and livestock deaths involved deep pits in enclosed swine or dairy buildings. Because H2S is heavier than air, it accumulates in low areas like pits and along floors. Common situations have included entering pits to perform maintenance work or retrieving objects that fell through the slats. Many incidents resulted in multiple fatalities involving unprotected, would-be rescuers (often family members), who didn’t recognize the hazard. H2S caused fatalities have also occurred in and atop liquid manure tanks used in field application.
Recent Fatalities
- 2013:
- Iowa: Jeremy Schulte (36), a custom applicator, died when he entered his tank to address equipment malfunction.
- 2015:
- Wisconsin: Rodney (47) and Jeremy (21) Seibel died after Rodney entered a pit to retrieve a piece of equipment that had fallen in; Jeremy attempted to rescue his father.
- Ohio: Humberto Hernandez (31), a custom applicator, was overcome while atop a tanker that was being filled with liquid manure.
- Iowa: Gene (58) and Austin (32) Opheim were repairing a manure pump when Austin entered the pit to retrieve fallen equipment; Gene entered to rescue his son.
- 2016-2017
- Wisconsin: Jonas Hoover (16) died when he entered the empty tank he’d used to fertilize a field.
- South Dakota: Lonnie Martinmaas (58) entered a dairy barn pit to do repairs; he was found and retrieved by brother, Rick (60), who was also overcome and never regained consciousness. Lonnie also died a few months later.
- Also in 2016, deaths occurred in new scenarios that had not previously been identified as dangerous: an open-air lagoon and slat-over-pit beef cattle barns.
- Mike Biadasz (29) died while agitating manure at an open lagoon on his family’s beef feedlot in Wisconsin. Sixteen cattle were also killed.
- Later in the fall, dozens of cattle were killed in separate incidents in Wisconsin, Iowa, and Illinois during pumping operations. Responding to these incidents, safety personnel measured field application concentrations as high as 100 ppm, with spot checks over 300 ppm during pumping.
Poor-quality well water and high sulfur containing dietary ingredients (distiller’s grains, gluten, and syrup) can increase sulfur excreted from animals, resulting in greater production of H2S and increased risk during manure handling. Environmental conditions including temperature, wind currents, supplemental ventilation, and agitation/stirring practices also affect the release rate and dispersion of H2S during manure handling.
Despite known contributing factors, there is no formula to accurately predict risk versus no risk. Unfortunately, past performance, building configuration, or work experiences of safe pumping do not predict future safety. In fact, most accounts of animals down or lost and human fatalities occurred after many prior, successfully uneventful experiences. “Never had a problem before” may be a reason producers mistakenly presume that the risk doesn’t apply to their own building or operation.
Gas Monitors
The only way to know when conditions become dangerous is to use direct-reading gas monitors that are specific for H2S. Many options are available from a variety of manufacturers. Options range from low-cost, small, single-gas, personal H2S monitors that can clip to the collar to multi-gas, data logging monitors that read H2S, oxygen, explosive gases, and carbon monoxide (or other gases, depending on sensor selection). All provide continuous detection with audible, vibrating, and visual alarms that alert the wearer to leave the area to fight H2S
Single-gas H2S personal monitors are the most basic and least expensive, featuring audible and visual alarms that respond at pre-set concentrations. The easiest to use models have a 2-year sensor life and are virtually maintenance free. The least expensive models simply display ‘service life remaining’ (in months) but have no concentration readouts. They must be replaced at the end of their service life. For manure handling activities, we recommend the next grade up; models that display H2S concentration in ppm when gas is present (and service life remaining, when no H2S is detected).
Two examples are GasClip Technologies SGC-Plus (SGG-P-H) and BW Clip Real Time H2S. These models display ppm up to 100 (IDLH concentration) which gives valuable information to see concentrations in real time and trends of increasing or decreasing levels. These are particularly useful since concentrations change rapidly during pumping and with distance from the source. Visual and audible alarms with real-time concentrations alert the wearer to leave the area. These models can store the date and time of alarm “incidents” and “over limit” events. With accessories, these events can be then be downloaded to a computer.
There are other models of single-gas H2S, personal monitors that require more maintenance; needing replaceable or rechargeable batteries.
If you plan to use a gas detector for additional applications like confined space entry into bins, pits, tanks, or other enclosures that may have limited oxygen or other toxic gases, then a multi-gas detector is more appropriate. Multi-gas or 4-gas monitors have sensors to detect oxygen, carbon monoxide, explosive gases, hydrogen sulfide, and other toxic gases, based on sensor selection. Remember that entry into any of these situations should only be done following confined space entry procedures; which may require the use of atmosphere-supplying respirators.
H2S and 4-gas monitors are available at local industrial safety supply stores and their online websites, as well as national online vendors including PKSafety, Grainger, Zoro, EnviroSafety, and many others. Stutsman’s also has monitors on hand for your purchase. Reach out to the waste handling team for more information.
Maintenance-free personal H2S monitors with ppm readout display and 24-month service life start at around $170-$220.
Bump Test: Know Your Monitor Will Respond When You Need It
Regardless of the type of monitor used, it’s critical to check that the sensor and alarms are working properly before each use in the field. Most manufacturers advise “bump testing” the monitor before each use. This means applying gas with a known H2S concentration to the monitor to make sure the alarms function and the sensor readout matches the canister concentration. If the monitor is not working, you want to know it before you need protection. Doing a bump test is like switching on your flashlight to make sure the bulb and batteries work before you take it into the dark basement during an outage. Gas canisters and tubing accessories for bump testing are available from the manufacturers and safety supply companies that sell gas monitors.
Pre-planning for manure handling means having monitors on hand and knowing how to use them. That’s just one part of the plan. Best safety practices also take into account environmental conditions, agitation techniques, communication, and awareness that the only respirator that will protect against the manure pit hydrogen sulfide emitted from the manure is an atmosphere-supplying (SCBA) respirator. It all starts with recognizing and respecting the hazard.
Fight H2S and Plan for Safety
- Make sure all employees, family, and visitors recognize and are aware of the hazard. Post signage and emergency contact information.
- Remove animals during agitation.
- Work with a partner and stay in communication.
- Use portable fans if available- intrinsically safe.
- Never get on top of or inside a tank to inspect.
- Open up the building to maximize ventilation (curtains/doors/window panels).
- Plan pumping when there’s a crosswind, 7-10 mph minimum.
- Bump check and wear personal H2S gas monitors (all personnel including field applicators). Alarms indicate concentrations rising fast – GET OUT!
- Cover or barricade manure pit openings to prevent falls into the pit.
- Use an area H2S monitor near pumps. Use it to control agitation speed & direction to keep H2S levels low. It also warns others from approaching.
- Shut off agitator when H2S levels rise over alarm setpoints.
- Use careful, slow agitation to avoid rapid high bursts. H2S is often highest at the onset of agitation and when pump nozzles are above the manure surface (rooster-tailing).
- Always keep agitation nozzles below manure surface. Don’t agitate with the top jet at or above the surface; this shoots H2S into the air.
- If manure is within 2’ of the slats, pump to draw down the volume before agitating; this will give some headroom for released H2S below the slats. Start agitating slowly after the manure level is at least 2’ below the slats.
- Stop agitating when manure level is within 6” of the bottom nozzle.
- NEVER get down to floor or slat level to inspect for problems.
Dealing with manure pit hydrogen sulfide is serious business, and safety is non-negotiable. Understanding the risks and having the right precautions, like using reliable H2S monitors, can be a game-changer. At Stutsman, we’re here to help. Contact us with any questions or concerns about staying safe just reach out.