CONFINED SPACE RESCUE: HAZARD AND OPERATIONS
Confined space rescues present dangers for rescuers as well as victims. Incidents involving confined spaces account for many injuries and fatalities each year. Occupational Safety and Health Administration (OSHA) statistics indicate that 60 percent of all confined space fatalities are rescuers.
Examples of confined spaces include wells, silos, dikes, pits, railcars, cellars, tank trucks, manholes, utility tunnels, tanks and vessels, culverts, caves, and large-diameter pipes and ducts. The generally hostile confinedspace environment presents various hazards including low oxygen levels, toxic atmospheres and surfaces, poor visibility, unstable footing, and access/ egress difficulties. The major hazards threatening rescuers may be categorized into three groups: atmospheric/ chemical, stored energy, and physical environment hazards.
The most significant grouping of dangers for the rescuer is atmospheric hazards—low-oxygen concentrations, toxins, and flammable substances. These hazards often prove fatal because many times they are invisible and not recognized. OSHA data indicate that the majority of confined space deaths and injuries are caused by atmospheric deficiencies or contaminants.
Low-oxygen concentrations. OSHA uses the term “asphyxiating atmosphere” to refer to an atmosphere that contains less than 19.5 percent oxygen—the established minimum acceptable level for atmospheric oxygen (the air we breathe in its purest form contains approximately 20.9 percent oxygen). Lower concentrations do not provide enough oxygen to supply our respiratory and metabolic needs.>
Oxygen levels in the atmosphere of confined spaces are affected by contaminants that reduce or displace oxygen. Oxygen also is depleted, through slow oxidation, by the rusting process, which often occurs in old equipment and vessels subjected to damp atmospheres, and by the presence of stores of damp carbon. Rapid oxidation, specifically fire, can use up oxygen as well. The fire could be accidental-such as one that occurs in an overheated bearing or an overloaded motor—or one that results from processes such as torch-cutting, welding, or brazing.
Oxygen is consumed in many natural biochemical processes that involve bacteria, yeast, and mold—generally found in confined spaces. Dangerously low oxygen concentrations are especially common in silos that contain fermenting silage or spoiled food products. The pharmacologically inert gases methane and ethane also are found in confined spaces. Always suspect the presence of methane any time organic matter has been allowed to decay over a period of time.
Remember, too, that the oxygen level in a confined space may drop to less than the minimum safe concentration simply as a result of the normal breathing requirements of the people within the limited space during a rescue operation.
The addition of any gas (other than oxygen) dilutes the oxygen in a eonfined space. The dilution effect is most noticeable with inert gases (gases that do not react to form any compound), as there are no effects (hazards) except at such high concentrations that oxygen reduction becomes an important factor.
The inert gas nitrogen* commonly is present in industrial environments. It is used to provide an oxygen-free atmosphere for oxygen-sensitive processes, to retard pyrophoric reactions, and to reduce the potential for fire in flammable storages. Nitrogen also has been used as a backup source of air for industrial pneumatic-control systems. Therefore, never tie your breathing apparatus into an airsupply system that is not specifically designated for and identified as breathing air. If nitrogen completely displaces oxygen, rescuers immediately will collapse and die.
Other industrial gases that are inert asphyxiates include the elemental “noble gases” (such as helium and argon; see “Chemical Data Notebook Series #72, lire Engineering, May 1992), carbon dioxide, and refrigeration gases such as the Freons®. Most of these colorless gases are heavier than air and therefore collect in low spots or at the bottom of tanks and vessels, making it difficult to ventilate the space and monitor gas levels.
Toxins. Chemically active contaminants— toxins —found in confined spaces may be encountered in gas, vapor, mist, dust, or fume form and are generated from a vast number of industrial materials such as cleaning solvents and acids, or are the result of chemical reactions, offgasing of sludges and solids, welding and other fire-related fumes, as well as combustionand internal-combustion engine exhausts. The contaminants may be high in the confined space due to lowvapor density, they may ride hot thermals generated by welding and burning, they may collect low in the vapor space due to high-vapor densities, or they may lurk around obstacles where air currents can’t effectively purge the space. Toxic, corrosive, radioactive, or biologically active liquid and solid contaminants may be on walls, in crawl spaces, or clinging to victims.
Contaminants have been categorized according to the following types of hazards:
- Irritants, which inflame mucous surfaces such as those in the upper respiratory tract, lungs, and terminal respiratory passages.
- Narcotics and anesthetics, which depress the central nervous system.
- Systemic poisons, which interfere with the biochemical reactions that maintain homeostasis.
- Particulates, small or sharp solids that work their way into body tissue.
- Corrosives, which destroy tissue. The physiological effects the toxins produce are independent of those caused by low oxygen concentrations. Some toxins produce immediate health effects; others cause delayed effects, which can take hours, days, or longer to manifest themselves; and still others cause immediate and long-term effects, depending on the concentration of the substance and the number and length of exposures. Repeated exposures to low concentrations of acrylonitrile, for example, have been implicated as a cause of cancer, while higher concentrations can produce various cyanosis-related symptoms—weakness, headache, convulsions, nausea, unconsciousness, and death—according to the amount of acrylonitrile encountered and individual tolerance level.
OSHA, in its proposed “Rule on Confined Space to Require Permits”— 29CFR 1910.146, defines confined space as “a space that is large enough to enter, is not designed for human occupancy, and may contain either a hazardous atmosphere or a material that could engulf the rescuer or has internal parts that could trap the rescuer or that contains any other unrecognized hazard such as exposure to energized electrical wires or moving unguarded equipment.
As of this printing, the proposed ailing has not yet been finalized. However, be aware that the proposal as currently written would require industrial facilities with confined space environments to establish an in-plant rescue team or have “an arrangement under which an outside rescue team will respond to a request for rescue serv ices” and also to make sure that the designated outside rescuers “are aware of the hazards they may confront when called on to perform rescues at the employer’s facility, so that the outside rescue team can equip, train, and conduct itself appropriately.”*
(Photos by author.)
t’lummable contaminants in their explosive ranges are another potential hazard of confined spaces. For an atmosphere to ignite and burn, the tire triangle must be established. The confined space atmosphere must have a flammable contaminant concentration in the explosive range —between the lower explosive limit (LEL) and upper explosive limit (l HI.), an oxygen concentration sufficient to support ignition and combustion, and an ignition source. The space must have materials that can burn and be above their ignition temperature, since below the ignition temperature the atmospheric concentration will be below the LEL.
Energy sources are serious hazards in confined space rescue. Electrical energy, in particular, has been a major cause of deaths and injuries, since many industrial processes rely heavilv on this power. Generators, transformers, and electric conduits are common in industrial confined spaces. Live wires, hanging or torn conduits, and poor or torn electrical insulation—often the case when construction or demolition work is underway at the site —increase the possibility that a rescuer will contact an electrified surface. Contacting an energized piece of metal could ground the rescuer to a portion of an electrical circuit, resulting in an electrical shock or even death.
While electrical energy hazards may be most obvious, the stored and kinetic energy of mechanical equipment used in industry represents a serious threat to health and safety. Moving and rotating heavy equipment; mechanical failures; breaking belts, gears, and motors; as well as other components all have been the means of misplaced mechanical energy. Limb entrapments and belts snapping under tension, for example, are not rare.
‘ITiermal energy is another significant cause of injury’ and death. Thermal conditions that can cause burns, frostbite, heat stress, and hypothermia are common to confined spaces. Vessel walls may have temperature jackets that contain hot water, steam, high-temperature oils, low-temperature water, brine, or low-temperature refrigeration fluids. Other temperature-control equipment that might be found in confined spaces includes steam coils, electrical-resistance heating, refrigeration components, fans, and direct-steam injection systems. Heated air rises and becomes trapped high up in confined spaces. Air temperatures exceeding 120°F taken into the lungs can cause a drop in blood pressure, failure of the circulatory system, edema, and irreversible tissue damage.’
PHYSICAL ENVIRONMENT HAZARDS
Physical hazards include those associated with limited opportunities for entry and exit; size of entry and exit points; limited size of the confined space itself; sharp objects; irregular, dirty, and slippery walking surfaces; shifting surfaces and stored flowing solids (sand, grain, gravel, and such); and poor visibility created not only by the absence of adequate light in some cases but also by unpainted surfaces, by beams, shafts, and equipment that break up available light, and by dust and other materials that fall into the space and scatter the light. All these factors restrict the rescuer’s ability to reach, treat, and remove the victim. Equipment may be difficult to maneuver in confined spaces. Utilizing the rescuer’s most basic safety equipment— the SCBA — could be a real challenge in light of the physical structure of the space. Engulfments, falls, and lacerations are hazards of the hostile physical environment of the confined space.
SCENE MANAGEMENT, SIZE-UP, AND SAFETY
As is the case with all rescues, rescuer as well as victim safety are primary objectives throughout a confined space rescue operation. Procedures should include the following:
- Immediately institute an incident command system.
- Appoint a safety officer who is familiar w ith the dangers the rescuers may face. The safety officer’s responsibilities in a confined space rescue are the same as those in a haz-mat incident: to make sure that all actions are carried out in a safe manner; to check equipment, safety lines, and breathing apparatus/air supply usage; to monitor activities, chemical problems, and properties, and to be sure that the Conduct the size-up. Actually, this evaluation begins as soon as the call is received. It entails determining the nature of the incident, how it is proceeding, how it can be resolved safely, whether preplans are available, and ascertaining the kinds of help that can be expected from the facility involved in the incident.
Once on the scene, obtain an accurate victim count. Determine whether haz mats are involved. Request qualified personnel to assist in material identification. Try to get as accurate an account of what happened as possible. Interview the individual who was nearest to the victim at the time of the accident. Get explicit details. Determine also whether MSDSs or drawings of the confined space are available; w hether the victim is alive and, if so, whether he/she is conscious; and how long the victim has been within the space. (Do not treat a body recovery as a rescue. Rescuers should not be endangered if the victim cannot possibly be alive.)
Make conservative judgments. For example, do not assume that a worker in a sludge tank fell off a ladder because of slippery shoes; he could have been overcome by methane or some other gas, or he could have been affected by an oxygen deficiency. When dealing with confined spaces, safety dictates that their atmospheres be considered hostile to humans until monitoring proves otherwise or until sufficient ventilation is provided and energy lockout accomplished.
- Formulate a safe plan of action based on a general understanding of the dangers usually associated with confined-space operations, a knowledge of the skill and experience levels of the personnel at the scene, an understanding of available background information, the current status of the involved confined space, and common sense. Weigh the safety risks for rescuers against the time requirements involved in rescuing a live victim.
- Monitor the environment to ensure that the dangers are controlled, conditions do not change during the life of the rescue operation, the situation does not deteriorate, and no new threats emerge. Monitoring involves estimating the potential dangers and which properties or qualities to measure.
- Wear SCBA (or an alternative breathing system) in confined spaces unless continuous monitoring proves that it is not necessary. An apparently breathing victim is not proof that the atmosphere is safe. Be prepared to return to SCBA should the material within the space be stirred or disturbed, which can regenerate atmospheric contaminants, or if conditions otherwise change. The safety officer must record the time each rescuer has been on SCBA and decide when each should come out of the space. Firefighter turnouts must be worn as minimum protection unless equivalent or more adequate protective clothing specific to the rescue is to be worn. The safety officer will decide when department SOFs must be modified, such as in instances when rescuers must wear less than full gear because of space limitations, environmental issues, or other conflicting needs.
- Clear all nonessential personnel from the scene to ensure the safety of rescuers and victims. At some confined space rescues, especially when construction is taking place at the site, on-site workers from the many crafts associated with construction already may have started rescue attempts before you arrive on scene. Too many people at the incident site could interfere with the operation and threaten rescuer and victim safety. Additional personnel with various needed skills should be held at staging areas until their participation is requested.
- Clear communications at confined space incidents are an absolute must for safety and success. Establish three-way communications between operations sector officer (at the point of rescue), safety officer, and incident commander. In addition, designated personnel directly involved in the operation who are observing the safety/progress of the rescuers should report to the safety officer.
Even if there is reasonable access to a confined space, safety demands that a lifeline be attached to each rescuer before he/she enters. The line tender or safety should be in continuous communication with the entering rescuer by hand signals, radio communication (if it can be safely used), or rope signals. (A generally accepted set of lifeline rope signals is “OATH,” which involves the following signals: O = 1 pull on the rope = okay; A = 2 pulls = advance line; T = 3 pulls = take up line; and H = 4 pulls = help.) The receiver must acknowledge the information.
- Evaluate the training levels and experience of the rescuers. Are the skills you need available? Are these firefighters used to working with SCBA in adverse situations? Are they knowledgeable about the medical aspects of the rescue? Can they operate while wearing a facepiece and carrying the rest of the SCBA or work with their SCBA suspended from overhead ropes? If ropes and safety lines are needed, do your personnel know how to use them? Have they ever rigged anything similar to what they must rig during this operation? Or, are the rescuers on scene emergency medical service personnel who know how to stabilize victims but whose only wearing of SCBA took place in a training class? Is the rescuer well trained in a particular piece of equipment? You may need to request industrial personnel to monitor operations or perform other important safety-related functions relative to specialized equipment. If you decide to use a “mixed” team, be sure that all members are sure of their responsibilities once they are inside the space. Thorough, frequent briefings are essential.
MORE OPERATIONAL CONSIDERATIONS
- Stabilize the confined environment. This step necessitates that the potential dangers be understood. Consider the following: If the danger within the confined area can’t be removed or stopped, can it be modified so that rescue personnel and the victim can be protected? If, for example, the heat can’t be shut off and the surfaces cooled down, can the hot walls and pipes be covered? If the piled material can’t be removed, will shoring keep loose materials from engulfing rescuers and victims? If atmospheric pollutants can’t be eliminated, can the atmosphere be cleaned by running smoke fans and forcing enough air into the space to overcome the contaminant concentration? If the atmosphere can’t be cleaned, then rescuers must wear air packs.
- In many confined space incidents, ongoing monitoring procedures are vital to safety. Monitoring devices should extend into the space well before rescuers enter. At least one individual must be directly responsible to the safety officer and report any changes reflected in the levels of monitored dangerous substances. These changes include a decrease in the height of the gravel pile, an increase in the depth of water or movement by the agitator shaft or conveyor belt, a decrease in the oxygen level, an increase in toxicity levels, or increases in organic levels or the LEE percentage.
Determine which monitoring approach to follow. Should the space be monitored once or at regular intervals? Are the measurements to be used to determine whether a rapid rescue attempt is indicated? If life safety is at stake, such as when rescuers enter a space that has reduced LEE, you must take continuous or frequent readings.
Oxygen concentration. Take this measurement first. The meter operator should know how to calibrate and zero the instrument and how to determine that it is operating properly. Elevated oxygen concentrations could cause ordinary combustibles to ignite more easily. Low oxygen concentrations will cause the organics to appear to be at a lower EEL than they actually arc. Subsequent ventilation of the vapor space then will increase the IJiL meter reading rather than, as expected, decrease it. That’s the reason the oxygen reading should be obtained first.
toxin levels!chemical concentrations. While an oxygen deficiency easily can be detected with an oxygen meter, testing for toxins is another matter; specific toxins require specific tests. Rescuers must have an idea of the toxins for which they should test. The meters for measuring toxicity levels (in ppm) are more readily available in some industrial settings and bulk-storage locations, some of which usually have meters that test within the lower ranges. Preplanning can help you to locate the meters available in your area and to arrange for their use when they are needed.
Continue atmospheric monitoring throughout the life of the incident and throughout the involved space and contiguous areas, including high points, low points, and the rescue and entry areas. Allow enough time for the meter to read the vapor sample. Training, drilling, and experience with the equipment being used are required to make accurate assessments.
Explosive (flammable) levels. Should the confined space rescue involve flammables or combustible contaminants in the atmosphere, the concerns become recognition and control. Recognition of these materials could be knowledge of the materials in the location or similar locations (preplans), or meter readings, or common sense (until disproved). There are numerous reasons that would lead a meter to indicate a negligible or low meter reading. Your faith in meter readings should depend on knowledge of the chemical and the meter.
LEL meters are calibrated only for one specific gas. A gas concentration that reads 60 percent LEL on a meter calibrated for methane might read 40 percent on a meter calibrated for hexane. Calibration factors for converting readings for one gas to readings for other gases are available from the meters’ manufacturers.
Some contaminants interfere with the monitoring of other contaminants and can cause readings to be inaccurate. The required meters or other sampling devices and individuals skilled in their operation and interpretation may be available at the plant where the accident occurred or a similar type of plant nearby. Preplan and work out assistance agreements with these locations.
After recognition comes control. Control may be accomplished by eliminating ignition sources, reducing the oxygen level to the point at which ignition won’t be supported (generally a difficult task), or controlling the contaminant at a concentration significantly below the LEL or above the UEL. (Typically, less than 10 percent LEL should be established before any consideration of entry is made.) Control of the atmospheric concentration of contaminants is the easiest method to employ. It also supports the victims’ need for oxygen.
We are used to thinking of ventilation as bringing a flammable concentration below the LEL, but realize that confined spaces, such as storage vessels, may have flammable concentrations well above the UEL. Under these conditions, ventilation initially would drop the contaminant concentration to within the flammable range rather than away from it. This underscores the need for an excellent understanding of monitoring techniques for flammable gases, both in testing potentially flammable atmospheres and interpreting the results, before further action is taken. When working with LEL meters, remember that while a reading of 10 percent LEL may be acceptable from a flammability standpoint, it still represents a concentration of 1,000 to 3,000ppm—a significant level for even moderately toxic materials.
Rescuers must understand the techniques for monitoring flammable gases, including testing potentially flammable atmospheres and interpreting the results before taking any further aetion.
- Be it through a manhole, a trap door, an inspection panel, a dome cover, a window, a crawl space— whatever —the means of entry cannot always be counted on as the means for exiting. The exit must allow for removing the victim expediently and not compromise victim or rescuer safety. Rescuers may have to create an exit by dismantling the enclosure, breaking out a wall, cutting an opening, or any number of different ways. When addressing safety, evaluate at least the following factors before creating an exit: Can it be created without structurally weakening the vessel or causing the space to fail? Is the atmosphere flammable, thereby excluding the use of devices that could be a source of ignition? Is the atmosphere toxic, and will the proposed exit subject others in the vicinity to these toxins? Will operations cause a potentially dangerous shift in stored granular solid material? Are we saving time by creating an exit? Are we compromising safety in any way?
- Movements should be made cautiously within the confined space. For instance, if a victim is entrapped bv flowing solids, the rescuer’s movements can bury the victim even further. The walkway’s surface may be bridged, as occurs when a granular solid is conveyed into the top of a vessel such as a silo and is unloaded out of the bottom; a void space may be formed between the solid bridge and the material that’s being drawn out of the vessel. Whenever possible, rescuers should not walk on granular surfaces. All rescuers and victims should be secured with belay and safety lines. Personnel should work off sheets of plywood or paneling or work from ropes when situations dictate.
- Lighting used in confined spaces should be explosionproof and should not produce much heat. Cover and seal the light so that water, other liquids, or vapors do not enter the lighting enclosure. Tie extensioncord connectors in an overhand knot, tape the male and female connectors, and hang out of the way of puddles. Use grounded wiring with groundfault interrupt protection.
- Always shut all electrical power (each voltage has its own disconnect) at the breaker panels or at the electrical disconnects. Remove all batteries from equipment. Some industrial electrical equipment charges capacitors (electrical storage components); the capacitors must be properly discharged to ensure that they have no electrical potential.
Controlling energy sources is important from the standpoint of making sure that conditions do not change during the rescue operation. Unplug any portable equipment that would injure or interfere with the rescue if the equipment were to start. Deenergize the disconnect (a switch gear that removes the power from the circuit); shut off the power at the power source; and lock the switches, breakers, or disconnects in the off position. Don’t rely on stop/start switches. A shutoff, even one with a bar through it, is not good enough, since many industrial circuits have parallel stop/start locations to allow turning on the equipment at other locations. The only other way to be sure that the equipment will not restart “on its own’’ is to have an electrician remove the fuses from the power circuit. Also, check the drawing of the electrical system to be sure there are no multiple electrical feeds. If the electrical shutoff can’t be locked in the “off” position, station a firefighter at the disconnect to make sure that no one attempts to turn the equipment back on.
The energy stored within belts, motors, gears, and other equipment components is much like the energy of a spring under compression. Site personnel should explain—ideally as part of preplanning—as part of on-site incident command planning how to stabilize and secure the equipment’s moving parts and how to release safely any energy stored within them before the rescue operation begins. When releasing any form of stored energy, always anticipate the reaction direction in which any stored energy will release. If you, for example, tried to cut a belt under tension to release a shaft, the cut belt would whip off the shaft as a result of the energy stored within it. A rescuer in the belt’s path could be injured.
- Drain temperature-control equipment, bring it to an ambient temperature, and turn the valve off to ensure that the temperature will remain under control. Also, lock the valves and chain them to protect victims and rescuers. Whenever the potential for high-air temperatures exists in a confined space, use self-contained breathing apparatus until the temperature is reduced by ventilation.
- Protect rescuers and victims by constructing physical barriers against the entrapping materials. For example, plywood sheets with 2x 4-inch cleats generally are used in trench rescues. Trench jacks or timbers, cut to size, are set on these sheets in the open portion of the trench. Digging then starts while rescuers are in the protection of this cage. In the case of a sand slide, plywood sheeting with suitable staking may be used above a victim’s location. Then, as the victim is dug out, he/she will not be covered with fresh sand. Fifty-five-gallon drums can be used tor side excavations. A 55-gallon drum with the bottom cut out can be jammed or jacked into the side of a hill and then dug out; the next 55-gallon drum, also with its bottom removed, is split down one side so that it just fits (telescopes) into the first drum. Each new section is worked through the preceding sections. Wood wedges with cuts to receive the drum edges provide structural support for the drum. Also, boxes can be built around entrapped victims to protect them from further slides. Dampening the material, if it is very dry, may help slow down the sliding of the material. Too much water, however, creates mud, which makes it more difficult to extricate the victim.
In the case of an entrapment in a vessel, isolate the confined space from any foreign material that might enter. Check and lock closed all valves attached to the vessel. Ideally, shut a second valve as well with a bleed or drain between the two shutoff valves. Do this for any line that contains dangerous materials. Other alternatives include installing a bland (a solid piece of metal) in the pipeline or disconnecting the line from the vessel. Many industries have confined space permits and plans you can follow to make isolating the vessel simpler. Drain nonhazardous liquids from the vessel unless it w ill cause floating or suspended solids to pack around the victim, making rescue more difficult.
- Many confined space incidents require that you move copious amounts of fresh air through the space. This can be done with smoke fans and ducting to serve as a channel that w ill direct the air. Have the fans push the air, to create positive-pressure ventilation, rather than pull the air, which creates negative pressure. Positive pressure mixes the atmosphere more uniformly. Using the fans as exhausters could “short-circuit” the ventilation process by drawing contaminants from other sources. It may also increase the evaporation of contaminants in the vapor space. Fans that might be subjected to flammable vapors must be approved under the National Electrical Code for use with the specific class and group of flammables in the atmosphere.
- Prepare plans for stabilizing and ultimately removing the victim. What is the extent of the victim’s injuries? What is the victim’s position? Is the victim breathing? Is the mouth and nose area unobstructed? Provide an air supply, if necessary, as soon as possible. If the victim is buried, dig— don’t pull —him out. If at all possible, do not attempt extrication techniques that could further injure the victim. Provide basic life support as soon as possible.
Determine which kind of packaging system to use. Long spine boards and basket stretchers may not fit into the confined space. Short spine boards tend to be too wide. Vest-type stabilization works well for confined spaces. Removing the victim safely also depends on the space’s physical layout, the available equipment, rescuer training, and local protocols. Determine whether the victim is stable enough to be transferred to a stokes basket. A SKED stretcher may work better in the restricted space. If the victim is not badly injured and is wearing a body harness, he could be lifted by the harness. Vertical extrication (hoisting the victim feet first using a modified girth hitch) is a method for removing victims that is gaining wider acceptance.^
Hopefully, this overview has made you more aware of the many concerns of confined space rescue. Knowledge of the hazards, extensive and ongoing training, a strong incident management system, undivided attention to scene safety , experience, preplanning, and ingenuity all will play a large part in your ability to handle confined space operations successfully.*
While nitrogen is considered to be inert, it will react with other elements under high heat.
- “Permit required confined spaces; Notice of Proposed Rulemaking. Federal Register: 54, 100, Monday, June 5, 1989, 29 CFR 1910.
- Elkins, H.B., The Chemistry of Industrial Toxicology, 1959. (New York: John Wiley & Sons, Inc.)
- “Essentials of Fire Fighting,” IFSTA, 2nd ed.
- Rescue Tech. 1:2, Summer 1990.