The Dangers of Gas in a Confined Space
Gas monitoring equipment is essential for confined space safety.
Dangerous gases and confined spaces are a dangerous mix. It can take only a few seconds for workers to succumb to a hazardous atmosphere, so there's no room for learning as you go.
Because of their nature, confined spaces often have a very different atmosphere than the one you'll find in a location designed for human comfort. Deadly gases can be trapped inside, organic material might decompose and release toxic fumes, and chemical reactions like rusting might crowd out the oxygen workers need to breathe safely.
Here’s the good news: when managed properly, workers can be protected against the harmful – and often fatal – effects of working in confined spaces. But it’s a team effort, and members at every level of the organizational must be involved in maintaining a safe work environment.
Atmospheric Hazards: What Are They?
There are three key types of atmospheres that pose a serious risk to confined space workers:
- Flammable and explosive
Flammable and Explosive Atmospheres
Flammable gases in a confined space can cause explosions, which can severely injure or kill workers. Flammable gas sources include:
- Natural gas from leaking gas lines
- Methane from decaying sewage
- Propane gas from leaking cylinders
- Vapor from solvents used for tasks like painting, cleaning, refinishing
Combine flammable gas with oxygen and add any kind of spark to the mix and you've got a recipe for disaster. Even if workers are not planning on repairing electrical equipment, sparks could still be a byproduct of using their tools while carrying out their regular work.
Toxic atmospheres are created when poisonous gases are present in the workspace. Since these gases are often colorless and odorless, they can be impossible to detect with our five senses. Workers who are exposed to high enough levels for lengthy periods can become ill, and some gases can even be fatal.
Many industrial products contain volatile organic compounds (VOCs). Proper ventilation is critical for any work areas in which these chemicals will be used.
Common sources of toxic gas include:
- Solvent vapors
- Hydrogen sulfide from decaying sewage or raw petroleum
- Carbon monoxide from engine exhaust
Oxygen-deficient atmospheres are those that contain less than 19.5 percent oxygen. Breathing this air can cause workers to lose judgment, coordination, and consciousness. In extreme cases, it can cause suffocation and death.
Oxygen depletion can occur in a variety of ways, depending on the type of confined space. Often, it involves displacement. In spaces such as holes and pits, gases that are heavier than air gravitate to the bottom and push the oxygen above.
Conversely, in elevated spaces like a shaft or at ceiling level, suffocation can occur when gases that are lighter than air rise to the top of the space and push the oxygen below the workers’ area.
Oxygen can also be used up by rusting metal, combustion, or bacteria-digesting sewage.
Common gas hazards in confined spaces
Several gases are frequently found in confined spaces and should be included in any effective confined space gas monitoring program.
Oxygen can be harmful to confined space workers in two ways: deficiency and excess. OSHA sets lower and upper thresholds for oxygen in the air that workers breathe and offers insight into the serious (and quick) impact that a lack of oxygen can have:
Minimum acceptable oxygen level
Decreased ability to work strenuously; impaired coordination; early symptoms
Respiration increases; poor judgment
Impaired respiration that may cause heart damage; lips turn blue
Mental failure; fainting and nausea; unconsciousness; vomiting
After 4-5 minutes: possible recovery
6 minutes: fatal 50% of the time
8 minutes: fatal
Coma in 40 seconds; often results in death
Oxygen enriched atmospheres can be just as harmful. At levels of about 21 percent, flammable and combustible materials can burn violently when ignited. Levels above 23.5 percent can be fatal.
Hydrogen sulfide, also known as sewer gas, is highly flammable. It's often the product of decaying organic matter and, while it is colorless and can't be seen, it has a telltale rotten egg smell. The effects on the worker depend on how much of it they breathe in and for how long, but exposure to high concentrations can quickly lead to death.
Since hydrogen sulfide is heavier than air, workers in recessed confined spaces like pits and storage tanks are most at risk. Those operating in sewers, manholes, and agricultural spaces should ensure their gas detector is in good shape and can accurately detect this poisonous gas.
Carbon monoxide is the single most common cause of fatal occupational gas poisoning. Since it’s odorless and colorless, it is impossible to detect without a gas detector and is particularly dangerous in confined or poorly ventilated spaces.
Carbon monoxide is produced by incomplete combustion, which makes it common in industrial environments where heavy propane or gas powered equipment like furnaces, vehicles, heaters, and boilers are running.
(Learn more about Carbon Monoxide: The Silent Killer.)
A Safe Rescue Is a Planned Rescue
It’s estimated that up to two thirds of would-be rescuers become victims. In light of this, employers need to spend time developing, reviewing, and rehearsing sound confined space rescue procedures. While it’s natural to want to rush to the side of a colleague in need, entering a hazardous atmosphere unprepared can worsen the situation and create secondary victims.
Employers should make sure they have at least one employee on site who is trained in first aid and CPR. All members of the rescue team should be trained to properly use the required PPE and rescue equipment. Since even trained rescuers have been injured or died while attempting confined space rescues, holding simulated emergency drills on a regular basis is highly advised.
(Learn about CPR Certification: Why You Need It, How to Get It.)
Monitoring for Gas in Confined Spaces
OSHA mandates a test of the internal atmosphere of a confined space with a calibrated direct-reading instrument before entry. The atmosphere should be tested for oxygen content, flammable gases and vapors, and potential toxic air contaminants – in that order. Unless the employer can confirm that periodic monitoring is sufficient, the atmosphere must be continuously monitored while the space is occupied. In either case, it must be re-tested prior to every entry.
Portable gas monitoring equipment for confined spaces must have, at a minimum, sensors for:
- Lower explosive limit (LEL)
- Hydrogen sulfide
- Carbon monoxide
Using gas monitors in confined spaces will help you stay compliant and avoid fines that can be as high as $126,749 per violation. Investing in proper gas monitoring equipment and practicing safe confined space procedures makes good financial sense. But it's real value is that it might just save lives.
For all things Confined Space, check out our Confined Space Knowledge Center.
More from AD Safety Network
- When should you consider using custom molded earplugs?
- At what height do falls become deadly?
- Who should be responsible for rescuing fallen workers?
- What kind of training do loading dock workers need?
- How often should I inspect a loading dock?
- How is wind chill calculated?
- What is the difference between occupational safety and process safety?
- Why should rubber insulating gloves be tested?
- What happens if I tie off at the foot level with a personal SRL?
- Why is testing with a NAIL4PET accredited lab important?
- What kind of face protection do I need when using a chainsaw?
- What is the permissible exposure limit (PEL) for silica?
- What is silica and why is it hazardous?
- Video Q&A - What is a safety policy?
- What kind of fire extinguisher is best for your work site?
- How do I choose the right respirator and mask for working with silica?
- Can I wear fall protection equipment over my rainwear or winter gear?
- When do I need a cage ladder?
- What types of gloves protect your hands from hazardous chemicals?
- How come I still got hurt while wearing flame-resistant clothing?
- How do I win over my most reluctant employees?
- What kinds of jobs should use disposable safety gloves?
- Is it true that safety shouldn't be a top priority?
- When are employers allowed to conduct drug and alcohol tests on their employees?
- How can I get employees more involved in the risk assessment plan?
- What are some of the indirect costs of workplace accidents?
- How often do fire extinguishers need to be inspected?
- What is the best way to store rubber safety gloves?
- How much voltage protection is needed for safety gloves used in electrical work?
- What is the difference between a safety valve and a release valve?
- When do workers have the right to refuse to work?
- What is the most overlooked item when designing Lockout/Tagout (LOTO) procedures?
- What are some of the misconceptions about heat stress and what should we do to address them?
- What tools should I tether when working at heights?
- What types of gas should I watch out for when working in a confined space?
- How do you create a culture of safety in your workplace?
- What is the difference between industrial safety and industrial hygiene?
- Is it important to get PPE assessments by trained professionals?
- What is a fault tree analysis?
- What kind of respirator cartridge should I use?
- What are the safety benefits of a whistleblower program?
- What type of safety record-keeping and recording should we be doing?
- What makes a hi-vis safety vest ANSI compliant?
- Why is it important to have air sampling done to determine my PELs?
- What is the life expectancy of fall protection equipment?
- What are some basic fall protection rules that each of my workers need to understand?
- How much clearance do I need to safely use a Leading Edge SRL?
- What is the difference between an acute hazard and a chronic hazard?
- What’s the difference between a bump test, a calibration check, and a full calibration?
- Is there any legislation regulating lone worker safety I should know about before hiring?
- What kind of fire extinguisher and accessories should be kept on hand on a factory floor?
- What can companies do to reduce their lost time injury frequency rates?
- Video Q&A - What's your safety network like?
- Video Q&A - What are the 3 levels of safety?
- Video Q&A - How do you treat a near miss?
- Does body weight affect falls differently?
- What ages are most affected by falls?
- Why do workers take risks?
- What Is the Difference Between OHSAS 18001 and 18002?
- What is the difference between lost time injury and medical treatment case?
- What is the difference between occupational health and safety and workplace health and safety?
- What is the difference between occupational health and occupational safety?
- What is the difference between a lost time injury and a disabling injury?