Whenever groups of hazardous materials responders get together, their conversation inevitably revolves around their most recent hazmat incidents. What was spilled, how big it was, how much damage was caused, and what they did to mitigate the incident are usually the main topics. Somewhere within the discussion someone will ask, “What level of PPE were you wearing?”

Often, you will hear the ‘Alphabet Suit’ response. “It was so bad we had to go in at Level A. Even the decon team was in level A.” However, does the alphabet suit system fully explain how we chose the proper personal protective equipment (PPPE)?

Determining the Need for PPE

In our training programs, we use the Benner D.E.C.I.D.E. model as a systematic approach to mitigating hazardous material incidents. The six-steps begin with detecting and identifying the chemical(s) involved in the incident. This is the key to any other actions that will be taken to favorably change the outcome of the incident. Without this information, anything that we choose to do is no more than a wild guess, which can lead to a disastrous ending.

Having identified the chemical(s) we move to the second step in the process, estimating the outcome of the incident without intervention. We need to answer the question, “If we stand back and watch this event play itself out, how bad could it be?”

Following the six stages of the event to its completion, we find ourselves identifying the potential harmful effects on the people, environment and properties that are impinged during the event. Any hazmat incident may have as many as six potential methods by which impingement will result in harm.

To identify these potential harmful effects we turn to resources that include the North America Emergency Response Guidebook (NAERG) and the Safety Data Sheet(s) (SDS), when available. It is the estimate of harmful effects that we must use to base our selection of the personal protective equipment (PPE) we will use.

The NAERG guides are broken into three sections: Potential Hazards; Public Safety; and Emergency Response. The potential hazards section is shown first and gives the responder a general idea of which harmful effects will be associated with the chemical. They are listed as either a ‘Fire or Explosion Hazard’ or as a ‘Health Hazard’. The most likely, or potentially greatest, risk will appear first. These should not be assumed the only hazards associated with the chemical. If we base our PPPE selection solely on this information, we may overlook other potential hazards.

The Safety Data Sheet(s) goes into much greater detail than the NAERG and should be considered the more reliable of the two resources. The SDS will spell out the limits for the levels of exposure (PEL; STEL; IDLH). The SDS will also provide recommendations for the PPE worn by employees working with the chemical on a regular basis.

It is at this point the responders must take care to identify all the potential harms that they could be exposed to during a mitigation operation. If we fail to identify them correctly, or we only concentrate on the ‘bad’ ones, we could be putting our responders at risk with an illusion that their PPE will fully protect them.

Alphabet Suits

The system of selecting PPE by the four levels of A-B-C-D is a quick and simple method of describing what responders wear when working with hazardous materials. Can we say that it will ensure the safety of the responders? What do the letters really mean? Let us look at what each level actually defines in terms of personal protection.

Level D, the lowest level of PPE, establishes the need to protect the responder from coming in direct contact with a chemical. By providing a chemical barrier, we isolate the responder from materials that could affect them directly when the chemical acts on their skin or exposes their eyes. It does not include airborne hazardous materials that may enter the body via the respiratory system, or oxygen deficient atmospheres. Level D means, “Don’t get it on you; Don’t need a respirator. Daily duties.”

Level C, the lowest level of respiratory protection, establishes the first level of respiratory protection. The potential for exposure by direct contact may be present as well. To select Level C the responders must not only identify the chemical(s) involved, but must also verify the levels of atmospheric exposure, including oxygen concentration. Level C assumes that the level of exposure will never exceed the assigned protection factor (APF) and that the oxygen content will never drop below 19.5 percent. Level C means, “Contact protection with a Cartridge respirator.”

Level B, the highest level of respiratory protection, establishes the point at which the atmosphere has reached a level that is immediately dangerous to life and health (IDLH). There may also be a contact hazard present, but the need for respiratory protection now mandates the use of atmosphere-supplied breathing apparatus OSHA 1910.134(d)(1)(iii) states, “Where the employer cannot identify or reasonably estimate the employee exposure, the employer shall consider the atmosphere to be IDLH.” Requirements for an IDLH atmosphere requires the respirator must be either:

1910.134(d)(2)(i)(A) A full facepiece pressure demand SCBA certified by NIOSH for a minimum service life of 30 minutes, or

1910.134(d)(2)(i)(B) A combination full facepiece pressure demand supplied-air respirator (SAR) with auxiliary self-contained air supply.

Level B means, “Bring Breathing air in a Bottle on your Back.”

Level A, the highest level of contact protection, based on the potential for an airborne contaminant to be absorbed through the skin. This presumes that at this level the respiratory hazard is IDLH, thus requiring an atmosphere-supplied breathing apparatus. This is supported by the fact that the protective suit must be gas-tight, thus creating a potential for an oxygen deficient atmosphere within the suit. Level A means “air-tight suit with its own Atmosphere inside for an Absorption hazard.”

So, there you have it. The Alphabet Suit System of selecting protective equipment. It seems so simple that anyone could use it to quickly select the PPE for an emergency operation. However, have we actually identified the PPPE? Have we incorporated ALL the potential hazards into our protective ensemble?

Have we addressed the ACTUAL hazards of the incident? For example, if we respond to a release of carbon dioxide, what is the PPPE? Based on the Alphabet Suit System, the potential for an asphyxiant atmosphere would require a Level B suit with an SCBA. Assuming there are no other hazards associated with this incident, what would a responder actually need to enter the hazard area? If there is no actual contact hazard that would require some level of protective garment a responder could enter wearing nothing except the SCBA. In this case, Level B could mean “Buck naked with Breathing apparatus.”

Proper Personal Protective Equipment (PPPE)

The Alphabet Suit System bases the entire selection decision on the chemical hazards, though asphyxiant hazards may be assumed whenever we choose level B or level A. Even though the Alphabet Suit System seems simple, it is not. If we do not fully address all the hazards and properly select all the elements of a protective ensemble, we may be setting ourselves up for failure.

Based on the estimated outcome in the D.E.C.I.D.E. process we have identified ALL six of the potential harmful effects of the chemical(s). Now, look at all six areas of the body that need to be protected. If there is an exposure potential for any of these areas, we must ensure that our responders are properly protected

If the primary hazard associated with the chemical(s) is fire or explosion, the selection of a chemical suit may be the wrong choice. In such a case, a Level A suit would also need to add an over-suit to protect against a flash fire, or a chemical suit which integrates a fire-retardant material as well as a chemical barrier. If such a suit is not available, the action plan to change the outcome must first focus on eliminating or controlling the fire hazard.

If the hazard assessment identifies mechanical hazards (i.e. explosion), the Alphabet Suit System offers us little or no guidance. Given that one of the leading causes of injury to hazmat responders is slips and falls, the Alphabet Suit System does not address that hazard.

We need to include the use of over-boots to provide protection against slips and falls, as well as protection against cuts and punctures when working around debris. Mechanical hazards also include falls from heights. When climbing ladders or working atop railroad cars there is no mention of personal fall arrest systems in the Alphabet Suit System. Don’t forget that we all have heads, and the use of a hard hat or helmet should always be included in selecting PPPE.

Decontamination PPPE

Any discussion of PPPE selection would not be complete if we ignored the requirements for the decontamination team. Going by the Alphabet Suit System, we have been trained to use the same level of PPE, or one level below the entry team. It assumes that the workers in the decontamination site are going to be exposed to the chemical(s) at the same quantity and concentration as the entry team.

If that is the case, then we must re-define our concept of the exclusion zone (hot zone). The exclusion zone is defined by the need to wear the highest level of PPE based upon the concentration of the chemical(s) and the probability that the responders will have direct contact with them during the mitigation operation. Assuming the exclusion zone is established correctly, there should be no need for anyone outside to wear any level of PPE.

When the entry team prepares to depart the exclusion zone it should be clearly implied that they have left the incident behind them, not dragged it out with them. That would mean that when they reach the boundary of the hot zone the only chemical(s) that would leave the zone are those that are upon, or permeated into, their PPE. Assuming that is correct, the level of exposure to the workers in the decontamination site would be minimal.

Given the actual hazard to the decontamination workers, the question of wearing an equal level of PPE to the entry team must be raised. If the entry team is wearing Level A suits, it only seems reasonable that the decontamination workers would need to wear Level A if there is so great an exposure that the air around them is IDLH.

Even if we step down one level, wearing a Level B suit still implies the atmosphere is IDLH. Rather than rely on the ‘simple’ system, perhaps we should more effectively evaluate the hazards and provide the decontamination workers with PPPE based on their actual expected exposure.


As hazardous materials responders we have an obligation to ourselves and those we are protecting to provide the highest degrees of protection for those people that are assigned to enter hazardous atmospheres and perform dangerous tasks. In our efforts to make the process of selecting personal protective equipment simpler, we may have left a chink in our armor.

No personal protective equipment can be assumed to provide safety if it not the proper personal protective equipment. The alphabet suit system can still be useful, but only when we ensure that we have identified and addressed all the potential hazards.           

John Lindstrom began his fire service career in 1976 and has been an adjunct instructor at the Hennepin Technical College (MN) since 1984.