Confined Space Rescue Operations

The federal Occupational Safety and Health Administration (OSHA) requires a written permit entry program to be established for confined space operations. What effect does this have on fire departments?

Photo by Bob Stella
Operating 250 feet under Boston Harbor during a tunnel rescue drill, firefighters begin walking some 1,000 feet to retrieve a "victim." Using only the lights on their helmets, the firefighters had to walk in sea water up to 10 inches deep that was leaking through cracks overhead as well as through machinery and such debris as bottles, wood and rocks. Confined space rescue operations should not be attempted unless all personnel are fully trained in their assigned tasks.

Some major fire departments interpret this to mean that no entries of a permit-required confined space for rescue operations shall be made until the fire department prepares and signs its own entry permit. In reality, the formal entry permit is used as an operational checklist to ensure firefighter safety.

OSHA specifies that the entry permit must contain the following information:

  • The space to be entered.
  • The purpose of the entry.
  • Date and authorized duration of entry permit.
  • The authorized entrants, by name, which will enable the attendant to determine quickly and accurately, for the duration of the permit, which authorized entrants are inside the permit space.
  • The currently serving attendants, by name.
  • The currently serving entry supervisor, by name, with room for the signature or initials of the entry supervisor who originally authorized entry.
  • Hazards of the permit space.
  • The measures used to isolate the permit space and to eliminate or control permit space hazards before entry.
  • Acceptable entry conditions.
  • The results of initial and periodic tests performed under the permit-required confined space program section.
  • The rescue and emergency services that can be summoned and the means (such as the equipment to use and the number to call) for summoning those services.
  • The communication procedures used by authorized entrants and attendants to maintain contact during the entry.
  • Equipment, such as personal protective equipment (PPE), testing equipment, communications equipment, alarm systems and rescue equipment to be provided for compliance with this section.
  • Any other information whose inclusion is necessary, given the circumstances of the particular confined space, in order to ensure employee safety.
  • Any additional permits, such as for hot work, that have been issued to authorize work in the permit space.

In most parts of the country, the fire department will be the lead agency in a confined space rescue operation, so a comprehensive program that assigns accountability, addresses formalized training and includes a written standard operating procedure should be in place.

Hazards/Hazard Abatement

Each confined space must be carefully evaluated for any hazards by the rescue team as the rescue plan is being developed. Consideration must be given to:

  • Atmospheric hazards.
  • Physical hazards.
  • Any other recognized serious safety or health hazards.

One of the most important aspects of sizing up a confined space operation is to understand the environment within the space. The leading cause of death in confined space incidents is asphyxiation due to oxygen deficiency; this is followed by exposure to toxic atmospheres. Approximately 30 percent of the injuries and 40 percent of the deaths in confined space incidents are caused by atmospheric-related problems.

To prepare for entry or to operate safely in a confined space, we must take into account the atmospheric conditions and protect ourselves accordingly. Until you prove otherwise, assume that all confined spaces have a hazardous atmosphere (this is easily remembered by the acronym FATE Flammable And Toxic Environment):

  • Atmospheric conditions are to be monitored before entry and throughout the time the confined space is occupied and shall include a test for stratifying levels of gas.
  • Conditions to be monitored are that of oxygen, hydrogen sulfide, carbon monoxide, flammable gas or vapors, toxic or poisonous vapors, and physical hazards.
  • Oxygen-deficient atmospheres will be considered to be levels of 19.5 percent or less. The use of respiratory protection is mandatory.
  • Oxygen-enriched atmospheres will be considered to be a level of 23.5 percent or greater. Again, the use of respiratory protection is mandatory.
  • OSHA defines a hazardous atmosphere as an atmosphere where greater than 10 percent of the lower explosive limit (LEL) of a flammable gas or vapor is present. Levels greater than 10 percent of the LEL require the use of respiratory protection and the proper tools and equipment for that environment. The LEL is defined as the lowest concentration of flammable gas or vapor of a material that can be ignited in air.
  • OSHA also requires a test for toxicity. Toxicity levels (measured in parts per million, or ppm) which exceed defined permissible exposure limits (PEL) create an atmosphere that is immediately dangerous to life or health (IDLH).
  • Airborne combustible dust that is at or exceeds its lower flammable limit is considered to be an atmospheric hazard. This is approximated when the dust obscures vision at a distance of five feet or less. Respiratory protection is mandatory in this environment.

Because some of the most common chemicals that create hazardous atmospheres within confined spaces are colorless, odorless and tasteless gases, failure to properly monitor the atmosphere before entry can be deadly to the rescuer. Atmospheric monitoring equipment should be properly maintained, carefully handled, and calibrated according to the manufacturer's specifications.

Flammable atmospheres are detected by measuring the percentage of the LEL. Most atmospheric monitors are calibrated with methane or pentane; they have conversion charts that will convert the monitor reading from methane to a specific gas. Different gases have varying lower explosive limits. If you are monitoring a gas with a different LEL than methane, and your meter is calibrated with methane, the meter will give you an inaccurate reading. You must use the conversion chart to obtain the proper atmospheric reading.

It is important to test the atmosphere in the following order:

  1. Oxygen.
  2. Flammability.
  3. Toxicity.
Photo by Glenn Drake/Philadelphia Fire Department Visual Communications Unit
Atmospheric monitoring is a significant part of a confined space rescue operational plan. This multi-function meter simultaneously monitors oxygen, carbon monoxide and combustible gases.

The first test will determine whether there is a normal or acceptable level of oxygen. One reason the oxygen level is tested first is because most combustible gas/flammability monitors are accurate only within a specified range of oxygen content. An atmosphere that is oxygen deficient or oxygen enriched may give a false flammability reading.

The initial tests of the atmosphere should be performed by an extension or remote probe before entry into the space is attempted. Every level of the space should be tested; some gases may stratify and give different readings at different levels of the space.

When monitoring for entries involving a descent into atmospheres that may be stratified, the atmospheric envelope should be tested a distance of approximately four feet in the direction of travel and to each side.

The final test is for toxicity. If you have knowledge of what chemical is in the confined space, you can use a "chemical-specific" monitor for that particular chemical. If you are dealing with an unknown chemical within the confined space, a special meter that narrows the spectrum of chemicals until it identifies the existing chemical(s) in the space must be used.

Atmospheric monitoring must occur throughout the rescue operation. Keep in mind that these situations are dynamic, and changes in the atmosphere can frequently occur due to ventilation operations, wind or humidity changes, stratification or other factors.


Once a hazardous atmosphere is identified, consideration should be given to ventilating the space. The primary goal of ventilation is to change the environment within the space to as "near normal" an atmosphere as possible. This can be accomplished by:

  • Decreasing the chance of an explosion or fire by eliminating the LEL of a flammable gas within the space.
  • Replacing a non-life-supporting atmosphere with an oxygen-sufficient, survivable atmosphere.
  • Eliminating the toxicity of the confined space by decreasing the ppm concentration of any toxic substance present.

It is advisable to use positive pressure ventilation to transfer safe air into and displace flammable and/or toxic vapors out of the confined space. Ventilation should be done to force air into the confined space by positive pressure instead of exhausting from the confined space. Exhausting from confined spaces may be appropriate at times in very specific situations to remove heavier vapors and gases that accumulate in lower areas but the introduction of fresh air should be established first and in greater cubic foot volumes. Purging of a confined space should be at a level to dilute the interior atmosphere sufficiently.

Confined space ventilation fans with extension ducts are ideal for this work. They are commonly used by utility companies when working in manholes and have an approximate 1,500 cfm rating. Standard smoke ejector-type ventilation fans with extension ducts (usually rated between 5,000 and 10,000 cfm) are also appropriate for confined space ventilation.

Careful consideration must be given to the environment with which you are dealing; you must be aware of potential explosion hazards and ensure that your ventilation equipment is appropriate for the atmosphere where it will be used.

Certain types of confined spaces may have built-in mechanical ventilation systems and fans that can be used to the rescuer's advantage. Any method available to increase airflow into and/or out of the space (such as additional entrance openings or manholes) should be considered.

As the ventilation operations progress, the atmosphere within the space is most likely going to change. It is critical to continually monitor the space and adjust your actions according to the most current environment within the confined space. If your ventilation efforts bring an atmosphere that was originally "too rich" to support combustion down into the explosive range, you must alter your operational plan accordingly.

Remember, the goal of ventilation is to change the environment within the space to a safe, life-sustaining atmosphere. The only way you can determine if your ventilation strategy is effective is by comprehensive atmospheric monitoring of the entire confined space area involved.

Physical Hazards

Physical hazards within confined spaces are usually easier to detect than atmospheric hazards, but can be just as deadly to the rescuer. All potential energy sources which might be present within the space must be identified and shut down prior to the rescue team's entry. Physical hazards exist in the form of:

  • Electrical, mechanical or hydraulic equipment which when activated can cause injury to rescuers operating in a confined space.
  • Engulfment and suffocation in loose materials (usually found in storage containers such as silos or hoppers) holding sand, gravel or grain.
  • Excessive noise inside of confined spaces can interfere with rescue operations by negatively affecting communications.
  • Objects falling into a vertical opening can strike rescuers.
  • Hot or cold temperature extremes within a confined space can severely affect rescue operations.
  • Release of any chemical material through supply or discharge lines which are a part of the confined space can cause an immediate deadly hazard.
  • Wet surfaces inside a confined space can cause falls and possibly increase the hazard of electrocution.

Lock-Out/Tag-Out Operations

One critical aspect of safely operating at a confined space emergency is referred to as "lock-out/tag-out." The OSHA Confined Space Standard specifically references lock-out/tag-out, and OSHA publishes a separate standard, Control of Hazardous Energy (Lock-Out/Tag-Out) [29 CFR 1910.147], which applies to any source of energy except electrical. Electrical energy lock-out/tag-out is even more specifically regulated by its own standard.

Photo by Glenn Drake/Philadelphia Fire Department Visual Communications Unit
An example of a keyed lock-out/tag-out device for a valve.

Although these standards are targeted primarily at industry as opposed to the fire service, many important points that apply to emergency operations at confined space incidents can be taken from them.

Unexpected, uncontrolled or accidental release of energy sources in a confined space can be deadly. A statistic from a recent study by the National Institute for Occupational Safety and Health (NIOSH) illustrates how dangerous uncontrolled energy sources can be: 59 percent of accidents caused by a release of energy during a maintenance procedure resulted in a death. This statistic is shown to convey to you the integral part the lock-out/tag-out procedure plays in confined space emergency operations.

While performing a size-up and developing a rescue operational plan, one of the main goals is to gather all relevant information about that confined space's energy sources and residual stored energy and then to ensure that lock-out/tag-out procedures are properly executed and operating personnel are protected from shortcuts, carelessness or mistakes due to a lack of knowledge. Established lock-out/tag-out procedures require the:

  1. Identification of all types of energy sources present (or potentially present) within the confined space and the shutdown of all related areas and operating processes.
  2. Isolation of all energy sources.
  3. Locking and tagging of all isolating devices.
  4. Final check and inspection of all the controls involved.

The most common energy sources found in confined spaces are chemical, electrical, gravitation, hydraulic, mechanical, pneumatic or thermal. Also, many confined spaces will have a secondary or multiple sources of energy present that will have to be shut down.

After all energy sources have been positively identified, the isolation of these sources must occur. This is usually accomplished by placing a lock or isolating device to physically block energy to the equipment or area being shut down.

Common examples of energy isolating devices are:

  • Electrical disconnects (electricity should always be isolated at the power supply or circuit breaker if possible).
  • Blanks, slide gates or slip lines (sometimes called "pancakes") used in pipelines to isolate chemical energy when it cannot be closed off or controlled by valves.
  • Blocks and pins used to prevent the movement of machine parts caused by pressure from hydraulic or pneumatic energy or gravitation.

When the identification and isolation of all energy sources has occurred, the locking and tagging of all isolating devices is the next step. Safety equipment suppliers manufacture lock-out supplies for every type of isolating requirement imaginable (such as valve and pipeline lock-outs, electrical plug lock-outs, circuit, fuse and wall switch lockouts), and most industrial settings will have these lock-out devices on hand.

A lock-out kit containing a basic assortment of these items should be carried by fire departments with the potential for confined space rescue operations. If your company arrives at the site of a confined space emergency and no lock-out equipment is available, one member of the company can be stationed at the energy source after it has been shut down to ensure that an accidental start-up does not occur. Under no circumstances should this member leave his or her position unless the device is physically locked out or the firefighter is relieved by orders of the incident commander. If the primary energy source shut-off is a substantial distance from the actual confined space incident site, coordination can be accomplished by communications via portable radio.

Once you are certain that lock-out has occurred, tags may now be installed in all areas required. These tags serve as a warning to anyone approaching the site that work is going on, and under no circumstances should energy be restarted to the affected area. This is an effective communication to subsequently arriving fire department personnel or for civilian workers on the site.

A final check and inspection of all the controls involved (such as valves, levers, start buttons, and switches) should now be accomplished. This final check will ensure that you have shut down the right machine or affected area and that any stored energy involved will be released. Only now will it be safe to proceed with the remainder of the rescue operation.

Extreme caution is the rule when performing lock-out/tag-out procedures: circuit breakers can be mislabelled or rewired, switches can fail, valves can leak. Assume the worst-case scenario, and never proceed until you are completely satisfied that the system cannot be operated and the space is neutralized from all energy sources. The goal of a proper lock-out/tag-out procedure is to eliminate accidental start-ups of equipment, electrical shock, and the release of stored energy or hazardous materials.

Start-up of energy sources after the confined space incident has been resolved is just as important as the original lock-out/tag-out procedure. Because of the potential dangers, under no circumstances should fire department personnel restore and start up machinery, equipment or energy sources. Due to the liability involved, start-up should be the responsibility of the affected party after the incident has been resolved (and any investigations required have been completed) and the scene is released.


Some of the most commonly encountered atmospheric hazards within confined spaces are made up of these five chemicals:


  • Colorless gas with the odor of rotten eggs
  • Widely used in industry
  • Irritant and asphyxiant
  • Dangerously flammable in high concentrations
  • Vapor density of 1.2
  • Will collect in depressions and at the bottom of a confined space
  • LEL of 4%


  • Formed by decomposition of organic materials (also known as marsh gas)
  • Colorless, odorless and tasteless
  • Likely to be found in sewer waste water and treatment systems
  • Considered a simple asphyxiant
  • Can displace oxygen if present in high concentrations
  • Vapor density of 0.5
  • Will be trapped in the upper levels of manholes, sewage-related and other confined spaces
  • Will explode when the gas/air mixture is 5% to 15% methane
  • LEL of 5%


  • Colorless, odorless and tasteless gas
  • Produced during the combustion of any carbon-based material
  • Chemical asphyxiant will combine with hemoglobin in blood and make the blood incapable of transporting oxygen through the body
  • Vapor density of 1.25
  • Will accumulate at the bottom of a confined space
  • LEL of 12%


  • Colorless, odorless and non-combustible gas
  • Produced during the combustion of any carbon-based material
  • Sometimes used as an "inerting" gas in confined space work
  • Introduced into the confined space in the form of "dry ice" to displace flammable gases and vapors
  • Vapor density of 1.5
  • Will collect at the bottom of a confined space
  • IDLH of 5%


  • Dark brown fuming liquid or vapor
  • Product of diesel engines, blasting and high-temperature welding
  • Will not burn but is an oxidizer
  • Vapor density of 1.6
  • Vapor will collect at the bottom of a confined space
  • IDLH of .005%

Fred Endrikat, a Firehouse® contributing editor, is a lieutenant and 22-year veteran of the Philadelphia, PA, Fire Department, assigned to Rescue Company 1. The first part of this series was published in the October 1996 issue.