|In the occupational safety arena, a commonly accepted “hierarchy of controls” exists that delineates the type of controls and the specific order in which they are employed to protect workers from hazards. The first method the hierarchy addresses is that of eliminating the hazard entirely. Next in line is the substitution of the hazard with a less hazardous activity or element. Engineering controls — such as installing guards on a piece of equipment with rotating parts — are next, followed then by administrative controls such as rotating personnel through the hazardous process to reduce the amount of exposure for any one employee. The final control is the use of personal protective equipment (PPE). The use of PPE is the last control in the hierarchy because it is the least effective method by which to protect employees. As hazardous materials responders, we are unlike our general industry counterparts in that for the vast majority of the time we do not have the luxury of utilizing any of the controls other than the use of PPE due to the very nature of our emergency response activities. The proper selection and use of hazardous materials PPE is therefore often the only thing that separates us from sheer disaster and should be treated with the importance and respect with which it is due.|
PPE for Hazardous Materials Response
When we bring up the subject of PPE for hazardous materials response, most personnel immediately think of hazmat suits. While the hazmat suit is a major element of the hazmat PPE ensemble, it is by no means the only component as it is but one link in the chain of defense. We will address those additional components later in our discussion.
Hazmat suits can be divided (as per the National Fire Protection Association) into two categories — splash protective and vapor protective. Just as the names imply, splash protective suits serve to protect personnel from liquid splashes, while vapor protective suits protect personnel from hazards in the vapor form in addition to liquid splashes.
In the United States, vapor protective suits are usually fully encapsulating while splash protective suits are usually not. Prior to personnel entering the hot zone, the compatibility of the suits worn with the chemical or chemicals that might be encountered should be thoroughly researched as suit manufacturers are required to provide compatibility data including the breakthrough time (the time from contact with the suit until detection of the chemical inside the suit) and permeation rate (the rate at which a chemical moves through the suit material on a molecular level).
Hazardous materials responders will often refer to a vapor protective suit as a “Level A” suit, however such terminology is misleading. The Environmental Protection Agency (EPA) defines the levels of protection provided by hazmat PPE (also sometimes termed chemical protective clothing or CPC), comprised of the combination of the suit type and respiratory protection worn. “Level D” PPE consists of a normal work uniform with no respiratory protection and does not provide any protection from hazardous chemicals. “Level C” PPE is comprised of a splash protective suit with an air purifying respirator (APR), which is a cartridge respirator designed to filter out contaminants from the atmosphere. A splash protective suit is also employed with “Level B” PPE; however, a self-contained breathing apparatus (SCBA) is worn to provide a higher level of respiratory protection. “Level A” PPE provides the highest level of chemical protection by consisting of a vapor protective suit and an SCBA for respiratory protection.
In terms of respiratory protection, APRs have a definitive set of limitations governing their proper use. The user has to know the contaminant or contaminants involved, as the cartridge or cartridges (some APRs use two cartridges) are designed to filter out specific contaminants. APRs cannot be used in oxygen deficient atmospheres less than 19.5 percent in oxygen concentration due to the fact that they do not add any oxygen to the mix, but rather just filter out the contaminants from the atmosphere that they are designed for. In addition, the user must utilize air monitoring equipment to determine the concentration of the contaminant or contaminants encountered to ensure that an APR is not worn in an environment in excess of the immediately dangerous to life or health (IDLH) concentration.
The IDLH concentration is the concentration at which the user will experience an immediate threat to life, escape-impairing symptoms or will suffer irreversible health effects. There are actually some instances in which an APR cannot be worn at concentrations even less than the IDLH value.
The Occupational Safety and Health Administration (OSHA) defines the maximum use concentration (MUC) for respiratory protective equipment as the product of the permissible exposure limit (PEL) of the contaminant and the assigned protection factor (APF), which is a numerical representation of the relative protection of a piece of respiratory protective equipment based on its type. For example, if we were to enter an area containing chlorine (PEL of 1 ppm) with a quarter facepiece APR (rarely used in present-day hazmat response with an APF of 5), the resulting MUC would be 5 ppm. The preceding results mean that a quarter facepiece APR could not be worn above 5 ppm of chlorine even though the IDLH of chlorine is 10 ppm.
Even though SCBAs represent the highest level of respiratory protection possible, such respiratory protection is not completely without restrictions and drawbacks. There is a finite air supply in an SCBA cylinder, and the actual duration that the air in a cylinder will last is dependent on the capacity of the cylinder, the fitness level of the wearer and the exertion level of the wearer. For example, a 30-minute SCBA cylinder may yield just 15 minutes of air if the wearer is exerting themselves very heavily. In addition, an SCBA imparts more of a burden on the user than an APR and if an SCBA is worn outside of chemical protective clothing (as in most Level B ensembles) a corrosive environment can affect the performance of the SCBA and even lead to failure of the exposed respiratory protective equipment.
Additional Hazmat Components
Let us now turn our attention to the additional components of the hazmat PPE ensemble. Hazmat gloves are integrated into vapor protective suits and are usually separate components of splash protective suits. In either instance, we need to ensure the compatibility of our gloves with the contaminants possibly encountered.
We should also be cognizant of the fact that we are, at a minimum, wearing at least a pair of medical gloves under our outer gloves, leading to reduced hand and finger dexterity. Hazmat boots are available in differing styles and their compatibility with possible contaminants must also be ensured. The sizing of hazmat boots is crucial in that if a splash protective suit does not have integrated booties the boot size usually is comparable to that of normal boots. In the case of a vapor protective suit or a splash protective suit with booties, the wearer should usually select hazmat boots that are two sizes larger than normal.
An additional PPE component that bears discussion is that of suit tape. We will usually tape up the zipper, glove/sleeve, pant/boot; and SCBA or APR/hood interfaces on splash protective suits and the zipper and flap closure on vapor protective suits to provide additional protection for the wearer. While we use duct tape for training purposes as it is inexpensive, we should never use it in real-world responses due to the fact it is not rated for chemical compatibility. We should instead use chemical tape that is designed for such situations and is accompanied with chemical compatibility data.
An additional area of discussion regarding vapor protective suits is that of flash resistance. Responders should not knowingly enter into a flammable atmosphere in hazmat PPE; however, there are instances in which the wearer needs protection from a possible flash fire environment in a vapor protective suit to allow them to escape if a flash occurs. With some vapor protective suits, a separate flash oversuit is needed, which adds a second face shield to look through and another layer of suit material to limit dexterity. Some modern vapor protective suits are, however, provided with a flash protective reflective layer that eliminates the need for a flash oversuit.
We also have updated our suit selection paradigm with the experience gained over the last 30 plus years of collective hazmat experience. In the “days of old” it was “Level A all the way” for entry into unknown environments. We now embrace the theory of risk-based response, which simply means that we match the level of PPE utilized with the level of the hazard encountered. If we can safely utilize Level B PPE instead of Level A PPE for example, the resulting lower burden placed on our personnel in terms of reduced heat exposure, greater dexterity and lessened fatigue will be welcomed by entry group personnel and will provide for greater levels of safety for entrants.
In conclusion, it is imperative as hazmat responders that we know how to properly select and use hazmat PPE, as well as recognize the limitations of such equipment. As we stated earlier, our hazmat PPE ensemble may be the only thing in between the wearer and certain disaster. In fact, the importance of hazmat PPE can be summed up in that we literally bet our lives on it every time we enter the hot zone.
As always, stay safe out there and be sure to visit the North Carolina Association of Hazardous Materials Responders website at www.nchazmat.com.