Confined Space Entry

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What is a Confined Space?
The OSHA permit-required confined space standard defines a confined space as a space that is large enough for an employee to enter, has restricted means of entry or exit, and is not designed for continuous employee occupancy. A permit-required confined space (permit space) is a confined space that presents or has the potential for hazards related to atmospheric conditions (toxic, flammable, asphyxiating), engulfment, conflagration, or any other recognized serious hazard.

Regulations governing entry into confined spaces are specified by OSHA. You can find these regulations at 29 CFR 1910.146. Examples of confined spaces include ship compartments, missile fuel tanks, vats, silos, sewers, tunnels, and vaults.


Confined Space Hazards
Dangerous vapors and gases can accumulate in confined spaces. Fires, explosions and physical hazards can also injure or kill an unprotected worker.

Physical Hazards
Physical hazards may result from mechanical equipment or moving parts, like agitators, blenders, and stirrers.

Other physical hazards include heat and sound. Temperatures can build up quickly in a permit space and cause exhaustion or dizziness. Sounds may reverberate and make it hard to hear important directions or warnings.

Oxygen Deficiency
The primary hazard associated with confined spaces is oxygen deficiency. Oxygen may be reduced in a space either by displacement or consumption. Oxygen is displaced by other gases such as argon, nitrogen, or methane. Consumption may be caused by chemical reactions such as rusting, rotting, fermentation, or burning of flammable substances.

Fire and explosion are serious dangers in permit spaces because fumes and vapors will ignite more quickly in the trapped air.

Toxic Air Contaminants
These contaminants occur from material previously stored in the tank or as a result of the use of coatings, cleaning solvents, or preservatives. Unfortunately, you will not be able to see or smell most toxins. They present two types of risk in a permit space. First, they can irritate your respiratory or nervous system. Second, some toxic chemicals can cut off your oxygen supply or get into your lungs and asphyxiate you.

Working in Confined Spaces

Before entering a permit space, all mechanical equipment must be locked out/tagged out and blocked against motion. All lines containing hazardous materials such as steam, gases, or coolants should also be shut off. Then you should test the air before entry as well as periodically as you work. Entry permits must be used for entry into a confined space that presents or has the potential to present hazards related to atmospheric conditions or any recognized serious hazard. In such cases, only a worker with a written permit should be allowed to enter a permit-required confined space. In situations where you must use permits, obtain a permit from your supervisor and post it outside the permit space to warn others that you are inside.
You should always follow safety procedures, your company’s permit-space program, and use protective equipment made available by your employer. Keep the following safety tips in mind:

  • Use prescribed personal protective and respiratory equipment at all times.
  • Test the air inside the permit space for flammable, explosive, and toxic vapors and gases before entry. If necessary, test again while work is in progress to ensure continued worker safety.
  • Always use spark-proof tools and explosion-proof fans, lights or air movers when working in permit spaces.
    Have trained, well-equipped workers standing by to rescue anyone who gets into trouble while working in a permit space.

Controlling Hazardous Energy
Use locks and tags to prevent accidental startup of equipment while someone is working in the permit space. Cut off steam, water, gas, or power lines that enter the space. Release all stored energy and block movable objects against motion. Use only safe, grounded, explosion-proof equipment and fans.

Testing The Air
Your company should have special instruments for testing the levels of oxygen, combustibility, and toxicity in a confined space. A common cause of injury and death in permit-space accidents is failure to test for dangerous air contaminants and safe oxygen levels. Test for oxygen and combustibility before you open the space by probing with test instruments near the entry.

Once the space is opened, test the air from top to bottom. Some gases, like propane and butane, are heavy, and they will sink to the bottom of the space. Light gases like methane will rise to the top. So you need to be sure to check all levels.

After you are sure that the oxygen level is adequate and there is nothing combustible in the space, test for toxicity. Notify your supervisor if pretests find hazards that you cannot adequately protect against. Follow-up testing may be periodic or continuous, depending on specific conditions. Because the work being done within a permit space may also change air quality, continuous testing may be needed to ensure worker safety.

Purge and Ventilate the Space
Some confined spaces may contain water, sediment, hazardous atmosphere, or other unwanted substances. These substances generally must be purged, that is, pumped out or otherwise removed, before entry.

Use ventilating equipment where possible. Ventilation should maintain an oxygen level between 19.5 percent and 23.5 percent and keep toxic gases and vapors within accepted levels prescribed by OSHA.

Where the entrance is large enough, portable self-contained breathing devices should be used unless the atmosphere is ventilated or has been determined to have no potential atmospheric hazards. If the entrance to a potentially hazardous atmosphere is too small, an air line mask should be used with supplied air. If there is any danger of disconnecting the air line, a 5 to 15-minute escape respirator containing breathing air should be carried. You might also need eye and hearing protection and protective clothing.

Rescue Procedures

At least one person should remain outside to summon help or offer assistance.  If the employer designates this attendant to perform rescue procedures in addition to monitoring the safety of the confined space entrant, he or she should be equipped with the necessary PPE and rescue equipment and trained in first-aid and cardiopulmonary resuscitation (CPR). He or she should maintain constant communication with those inside the space either visually, by radio, or by field telephone. If a situation arises that requires emergency entry, the attendant should not enter until additional help arrives.

A rope tied around a worker’s waist is not an acceptable rescue method because it does not allow a single attendant to pull an injured worker out of a space. A full body harness and lifeline is a better approach because it can be attached to a block and tackle which a single rescuer/ attendant can operate.

Strict adherence to safety rules will allow you to work safely in permit-required confined spaces.

KEMI does not assume liability for the content of information contained herein. Safety and health remain your responsibility. This information is to be used for informational purposes only and not intended to be exhaustive or a substitute for proper training, supervision or manufacturers’ instructions/recommendations. KEMI, by publication of this information, does not assume liability for damage or injury arising from reliance upon it. Compliance with this information is not a guarantee or warranty that you will be in conformity with any laws or regulations nor does it ensure the absolute safety of any person, place or object, including, but not limited to, you, your occupation, employees, customers or place of business.