Because of the speed with which a worker can become incapacitated, confined spaces require more safety considerations than typical work sites. Anyone entering a place without adequate ventilation must take precautions for their safety. This is especially true for confined spaces where pooling gases or lack of breathable atmosphere combined with difficult entry and exit can prove fatal.
The Occupational Health and Safety Administration (OSHA) has developed guidelines for safety before and during work in confined spaces. We have broken these rules into what we consider the top 10 basic considerations for anyone about to enter a confined space.
1. Is This a Confined Space?
Knowledge in the case of confined space entry is power. One of OSHA’s main requirements for industrial sites states that all confined spaces should be clearly marked as ‘off-access’ to any personnel without a written permit. For sites without clearly defined permit-required confined spaces, all areas that have limited access, are not built for human habitation (such as tanks, silos, sewers etc.), that may be able to hold dangerous gases or liquids, or that contain a product or substance that could engulf a worker (grain in a grain elevator for example) should be treated as a dangerous confined space.
Part of the danger with confined spaces is that they often appear to be harmless. It is impossible to see a lack of oxygen for example. Workers must be aware of the dangers that can reside in these areas. These include, but aren’t limited to: lack of oxygen, build-up of harmful gases, accumulation of explosive gases, and difficult entry and/or exit.
Being able to recognize the potential danger in a confined space is the first step to staying out of harm’s way.
2. Is the Atmosphere Safe?
Without oxygen, a worker in a confined space will be dead in 4 minutes. Testing for oxygen levels and other common dangerous gases is imperative for worker safety in a confined space environment. Ideally this is done before workers enter the space.
A multi-gas detector with an internal pump (or a detector that works in tandem with a manual pump) can test the air in a confined space to determine the safety of the atmosphere before workers enter. Testing must be done in several levels of the space because specific hazardous gases react differently to the rest of the atmosphere. Why? Hydrogen Sulfide is slightly heavier than air, so it tends to sink to the bottom of a tank or other space, while other dangerous gases (such as methane) may be lighter than air and rise to the top. Only by testing all levels of the tank you are about to enter can you be reasonably sure the atmosphere is acceptable for breathing.
Gas monitors typically check for the following:
• Oxygen (O2) Levels High/Low – Low oxygen levels make breathing difficult and workers become sleepy or lack strength. Extremely low levels will cause a worker to collapse and suffocate. High concentrations of O2 aid combustion and flammability and are therefore also highly dangerous.
• Carbon monoxide is a toxic gas which replaces oxygen in the blood stream when breathed in and immediately starts destroying cells and oxygen-starving vital organs. Even high concentrations of CO are tasteless and odorless and can render a worker unconscious in a very short period of time. If a flame is present, carbon monoxide is also flammable at high concentrations when combined with air.
• Hydrogen sulfide, also known as “sewer gas”, is characterized by a strong rotten egg smell, and is both flammable and toxic. Prolonged exposure deadens the ability of the worker to sense the strong odor, and can lead to severe breathing problems and respiratory failure. H2S is dangerous because it can incapacitate a worker with only one breath and have them on the ground in seconds. High concentrations will completely starve vital organs and can kill quickly.
• Lower Explosive Limit (LEL) – This is the level where combustion can occur from gases produced by a variety of organic compounds that mix with oxygen. This dangerous mixture can be ignited by open flame, arcs from electrical equipment, and very hot surfaces as well as from less obvious sources such as static electricity and friction sparks. The level or concentration of explosive gas required for an explosion varies by the type of gas. For instance, Propane and Methane reach their LEL at different concentrations. If possible, your instrument should be calibrated for the gas you expect to encounter.
If any one of these adverse conditions is found you must mitigate them before entry can take place (usually via forced ventilation or tank cleaning).
3. How Do I Exit Safely?
Before you start thinking about entering, first make sure you can get back out.
Ask yourself: Will I be able to get back out unassisted under normal circumstances? Will the equipment I am carrying make movement within the confined space more difficult? Will my equipment hamper my exit of the space if I am injured? Do I have someone in place who will know what to do to get me out if I am incapacitated? Has your team practiced emergency evacuation techniques?
Something else to think about: supposing there is a plan for exiting of the confined space – has anything changed with regards to the confined space itself, or to the equipment used that may alter those plans? If so, adjust the plan and make sure the team knows what adjustments have been made.
If you don’t have a plan for exit, don’t enter.
4. How Do I Enter Safely?
Nowhere is the phrase “plan your work and work your plan” more applicable than in confined space entry.
Once you have determined the atmospheric safety of the space, and know your plan for a quick exit in the case of an emergency, you are ready to enter the space and complete your work. Depending on the specific entrance, workers may be lowered with block and tackle, or they may be able to climb in unassisted; there may even be an access ladder inside the space. Whatever the case, all work and movement in a confined space should be deliberate and methodical with a constant awareness of personal safety at all times. Personal gas monitors must be checked to see they are working, and many have a display that shows workers this information.
A full-body harness with a cable attached to an external anchor point and winch can allow non-entry retrieval of your body should you become incapacitated. Your chances of survival if a team member can immediately begin to extract you at the first signs of trouble are exponentially better than an entry rescue or rescue from emergency services. Keep that in mind if you are planning on staying alive.
5. Will The Atmosphere Stay Safe?
Once you’ve established that the atmosphere is safe to enter, you next have to know that it will stay that way. Often the work conducted in a confined space contributes to degradation of the breathable atmosphere. Welding or gas powered pumps, for example, can increase dangerous gas levels, and venting may not entirely erase the gas or fume dangers.
Equipment that normally operates within specific confined spaces such as fans and turbines must be locked out (turned off and not able to be turned back on) while work is being completed. A motor that is not intrinsically safe (i.e. may produce a spark or ignition in the right circumstance) can cause a fire or an explosion if, for example, workers are painting with flammable epoxy-based paint without adequate ventilation.
Sometimes the work being completed can affect the quality of the air: groundwater mixing with chalk or limestone can produce CO2 that displaces oxygen; welding creates nitrogen oxide and carbon monoxide which can do the same thing. In maritime operations a ships hold may become toxic if cargo ruptures because of movement of the vessel. Dangerous atmospheres can quickly develop when different chemical compounds come together and create a reaction or when heavy gas has nowhere else to go, and begins to overwhelm the breathable air.
There are a variety of site-specific considerations that need to taken into consideration while work is progressing. Tanks and silos have their own unique dangers where solidification of grain or flour which can create ‘bridges’ with voids beneath that can collapse when disturbed or stepped upon. A collapsed bridge can easily engulf a worker in a split second, where they can quickly suffocate. Constant gas detection and vigilance to potential danger should be used at all times.
Most multi-gas detectors are available with long-life batteries that last for hours, emitting audible alarms as well as flashing lights and vibration alerts for noisy work environments should adverse or long-term gas exposure be detected. It’s important to know where other members of your team are working, and if an alarm sounds, be ready to get out quickly.
6. Does the Space Need Ventilating?
If the air is found to be unsafe within the confined space because of existing fumes or gas, or if the work being done will contribute to a degradation of the breathable atmosphere, the space needs to be ventilated.
The most common way to replace the air in a confined space is with targeted ventilation performed with a portable blower combined with ducting. This allows the air in the confined space to be quickly and continuously replaced in the area where your team is working.
To learn how to correctly ventilate a confined space, click here.
7. Equipment Check
It’s important to check your equipment before beginning any sort of confined space entry work. Has your gas detector been bump-tested or recently calibrated? Have all lines been checked for wear? Have harnesses been properly stored? Have they been involved in a significant accident that would reduce their reliability? (If so, discard them!) Does the retrieval winch need to be serviced?
All Emergency Rescue equipment should be ready and at hand, even if you hopefully won’t be using it. If you are stuck in a confined space unable to breathe, the last thing you want is your non-entry assistant having to run back to the shed for equipment.
Confined spaces are often cramped, dark and awkwardly shaped. A well-lit worksite helps workers avoid injury. Remember that lighting in confined space around potentially combustible gases should always be intrinsically safe with no chance of setting off an explosion or flash fire.
A number of companies make intrinsically safe lighting. For personal, hands-free lighting, see the industrial-rated Pixa headlamps from Petzl.
Worker safety equipment continues to improve. Some of the newer gas monitors have “man-down alarm modes” which sound if the monitor’s internal motion detector has been motionless for more than its set amount of time. In effect, this alarm allows workers to communicate with other team members even if they are incapacitated.
Additionally, wireless communication can often (but depending on the confined space, not always) alert remote safety team members if there is a problem. By sounding the “man-down alarm” remotely at an operations headquarters, this technology allows team members to start emergency procedures even if they are not close to where the emergency is occurring.
Regardless of the technology, nothing can replace having a stand-by worker positioned at the exit when workers are in a confined space. This tried and true system allows the outside person not only to communicate with workers within the space but also to call for help if it is needed. Additionally, it places a non-entry rescue person at the focus point to initiate rescue of a trapped worker.
10. Are you and your crew up to the task?
Since it may be your life the individual team members hold in their hands, are you comfortable with their grip? Confined spaces can be much more physically demanding than regular work areas. Not only can they be difficult to navigate, but changes in the air composition can make them an increased risk for people with asthma or who are heavy smokers.
A team leader needs to be brutally honest about the physical and mental fitness of crew members he sends into confined space situations. Can each team member be relied upon in a life-threatening situation? Are there drug problems or attention deficit disorders which may affect the safety of the entire crew? If you know of problems such as these and opt to send the team anyway, you may be held to account for any accidents that occur. It is worth considering.
Confined space safety is an ongoing process that will not be perfected until no worker is injured or killed in these inherently dangerous environments. This list is not meant to be comprehensive (check the OSHA Standards for that), but rather a starting point for anyone needing to do maintenance, repair or inspection of confined space.
The greatest danger in confined space work lies in underestimating the potential life-threatening hazards that may lurk in very neutral-seeming surroundings. Stop to consider the dangers before you enter, and be mindful that confined spaces can become dangerous after you have entered. We hope this list may inspire you to review your safety plan and make adjustments that could potentially save a life.