The Hazards of H2S Gas (hydrogen sulfide)
Table of Contents
The Hazards of H2S Gas (Hydrogen Sulfide)
What is hydrogen sulfide (H2S) gas?
Where is H2S gas found
Symptoms of H2S gas exposure
What are the hazards and risks associated with H2S gas exposure?
The deadly numbers and statistics from H2S gas
Lone workers and H2S exposure
Who is at risk of being exposed to H2S gas?
What are the long-term effects of exposure to hydrogen sulfide on a worker’s health?
How fast can H2S gas kill you?
What can be done to mitigate H2S gas hazards?
Detection equipment for hazardous gas
Additional resources for workplace safety
Protect your team from invisible threats
The Hazards of H2S Gas (Hydrogen Sulfide)
Hydrogen sulfide gas is a deadly occupational hazard for workers. It is one of the leading causes of workplace gas inhalation deaths in the U.S. and according to the Bureau of Labor Statistics (BLS), hydrogen sulfide (H2S) gas caused 46 worker deaths between 2011 and 2017.
But what makes H2S so dangerous to employees and lone workers? Even at low concentrations and levels, H2S is highly toxic and flammable. But additionally, it is heavier than air and can travel along the ground, accumulating in confined spaces such as poorly ventilated areas, manure pits, sewers, manholes, and underground vaults.
What is hydrogen sulfide (H2S) gas?
H2S gas is a chemical compound that stands for hydrogen sulfide carbonyl sulfide gas. It is a colorless gas and is commonly recognized for its distinct rotten egg smell. H2S gas is also widely referred to as sewer gas, sour gas, stink damp, or hydrosulphuric acid. H2S gas is extremely poisonous to humans, corrosive, and very flammable. When it burns, H2S gas emits another deadly gas: sulfur dioxide, which has similar symptoms and outcomes to H2S gas exposure. Unfortunately, year after year workers are incidentally exposed to H2S gas, many of whom suffer detrimental consequences since an unsafe amount can kill a worker in under 10 seconds.
Where is H2S gas found
H2S gas is soluble in water and oil. It could be released anytime the substance is heated or depressurized. It is found in crude petroleum, natural gas, mineral rock formations, and hot springs. Therefore, the drilling and extraction of crude oil and natural gas creates hydrogen sulfide gas emissions. It may also be present when bacteria in organic materials or human/animal waste are broken down in the absence of oxygen. Industries that produce the most substantial amounts of H2S gas include:
Wastewater treatment
Oil and gas drilling
Mining
Paper mills
Tanning and dye production
Agriculture (manure pits)
H2S is heavier than air, it tends to settle in low-lying areas, making confined spaces particularly hazardous. Areas with poor ventilation, such as sewer lines, manure pits, or basements, are likely places for H2S gas to collect and sit. Other settings where H2S gas may be a concern include the breaking down of wood into pulp, working in swamps or landfills, and in mining situations where mineral rock is present.
Symptoms of H2S gas exposure
H2S gas can be deadly even in the smallest quantities, and significant levels of the gas often kill the victim’s sense of smell. Therefore, the distinct “egg odor” should not be used as a measure of how much H2S gas is present. A worker can find themselves in a fatal situation in mere seconds. If there are low levels of H2S gas present, the following symptoms may occur:
Eye irritation
Coughing
Headache
Nausea
Disorientation
H2S gas is so toxic that a small amount can kill a worker. Thus, any symptoms that may result from even the lowest level of H2S gas should not be taken lightly.
Important: Loss of smell does not mean the gas is gone—it may indicate dangerously high exposure.
What are the hazards and risks associated with H2S gas exposure?
H2S gas is considered an irritant and chemical asphyxiant, which is any substance that inhibits the flow of oxygen from our bloodstream to our cells or prevents cellular respiration even if there is ample oxygen in the immediate environment. In other words, H2S gas can effectively stop a worker’s ability to breathe when the lungs absorb the gas. Depending on the level present, H2S exposure to health effects include irritated eyes, a running nose, and coughing. If the levels increase, the consequences are increasingly severe, with side effects mentioned previously beginning to occur, like dizziness and nausea to death within seconds.
It should be noted that even short-term exposure to hydrogen sulfide can lead to respiratory distress, while long-term exposure may cause neurological damage.
The deadly numbers and statistics from H2S gas
800 ppm (parts per million) is the lethal concentration from five minutes of exposure. Concentrations over 1000 ppm cause immediate collapse with loss of breathing, even after inhalation of a single breath. For comparison, carbon monoxide poisoning typically requires longer exposure to reach fatal levels – H2S can kill in seconds.
Lone workers and H2S exposure
Who is at risk of being exposed to H2S gas?
Without immediate access to help, lone workers face increased risks from H2S exposure, especially in remote or poorly ventilated areas.
Lone workers who are most likely to be exposed to unsafe levels of H2S gas include those employees who are required to work in small or confined spaces with poor ventilation, such as those in the oil and natural gas industry. But also, a construction worker entering a drainage ditch, for example, could encounter H2S immediately and be unable to react in time. Employees working with any ignition sources are also at risk because of the flammable nature of H2S. Furthermore, the gas is extremely explosive and can be triggered near cigarettes, pipes, or even matches.
An environment that has “still air” is also risky. Anywhere that does not permit the free flow of fresh air can result in a gas collection that can very quickly build to a toxic level. Lastly, employees who are not educated on the warning signs of the presence of H2S gas are most at risk. This could include any workers across all industries. Protocols should first and foremost educate workers on the importance of a respiratory device when inspecting an H2S leak or rescuing a co-worker. Being aware of the warning signals, symptoms, side effects, and protocols could save your life and the lives of your co-workers.
What are the long-term effects of exposure to hydrogen sulfide on a worker’s health?
Prolonged inhalation of H2S gas can cause serious injury to a person’s central nervous system, at high concentration a person can suffer unconsciousness, coma, seizures, and even death. Short-term exposure to H2S gas can cause headaches, nausea, and irritation to the eyes and skin.
How fast can H2S gas kill you?
H2S exposure is not something to be taken lightly. Within only five minutes, the worker will be at risk of staggering and collapsing. In 30 minutes, they will experience serious damage to their eyes. After only 30 to 60 minutes, they could experience death. According to an Annals of Saudi Medicine study:
“H2S is immediately fatal when concentrations are over 500-1000 parts per million (ppm) but exposure to lower concentrations, such as 10-500 ppm, can cause various respiratory symptoms that range from rhinitis to acute respiratory failure. H2S may also affect multiple organs, causing temporary or permanent derangements in the nervous, cardiovascular, renal, hepatic, and hematological systems.”
What can be done to mitigate H2S gas hazards?
So what can be done to protect your lone workers from this invisible threat? There are a number of steps that employers can proactively take such as:
Provide respiratory and personal protective equipment (PPE).
Provide an automated check-in system such as a lone worker safety app
All electronics need to be enclosed in an intrinsically safe case
Install explosion-proof and corrosion-resistant air and exhaust ventilation systems.
Train and educate your team about hazards and controls including the symptoms of H2S exposure and the protocols to follow if exposed.
Develop and practice emergency rescue procedures.
Detection equipment for hazardous gas
H2S detection equipment encompasses devices that detect and alert the worker of unsafe air quality through sound and vibratory alarms.
Many available devices have multi-gas detecting features and can spot several types of harmful gases and fumes when work is being performed. They range in price from hundreds to thousands of dollars, depending on the safety needs of your workplace. Disposable or maintenance-free gas detectors that do not require sensor or battery replacement are also available.
Thanks to advances in technology, H2S detection equipment, and tools are becoming smaller and more compact, allowing more lone workers to carry these devices into remote areas and tight spaces.
Additional resources for workplace safety
Hazards exist in every workplace, but how do you know which ones have the most potential to harm workers? By identifying hazards at your workplace, you will be better prepared to control or eliminate them and prevent accidents, injuries, property damage, and downtime. Assess and identify existing and potential hazards in your workplace with this free, effective hazard assessment guide.
Also, because lone workers face unique risks due to the isolated nature of their roles, here is a comprehensive lone worker policy guide to help organizations protect these employees. This intuitive document walks you through the process of developing an effective lone worker safety policy. From identifying lone worker roles to conducting hazard assessments and defining clear procedures, this guide will help prepare your team to work safely and confidently.
Protect your team from invisible threats
Hydrogen sulfide gas is fast-acting and deadly; but is also preventable. Equip lone workers with the valuable knowledge, technological tools, and safety protocols they need to stay safe.