Personal Protective Equipment (PPE) for NH3 Releases Less Than 15,000 PPM of Vapor



The federal Occupational Safety and Health Administration sets the safe work practice guidelines that employers must comply with as minimum standards. Many states have assumed administering authority and have the right to define a higher standard of safety, when local hazards and special conditions exist.

The information used to produce the recommendations in this document was gathered from federal OSHA requirements, ASTI-related experiences in handling anhydrous ammonia releases, and from related technical information about personal protective equipment, or PPE, standards.

Levels of response into environments containing ammonia vapor were defined in October of 1991 in an OSHA Standard Interpretation Letter written by Patricia K. Clark, Regional Director of Compliance Programs for OSHA. She was answering a question from a firefighter who wanted clarification on the most appropriate level of PPE to wear within ammonia vapor during an emergency event. Following is the key summary that Director Clark provided in her Interpretation Letter:

“Generally, we would expect emergency responders to respond in Level A suits to unknown concentration levels and levels at or above one-half the Immediate Dangerous to Life and Health, or IDLH, level. The IDLH for ammonia is 500 parts per million, or PPM, (now 300 PPM) and one half that level is 250 PPM (now 150 PPM). However, ammonia is an inhalation hazard at 1,000 PPM and not a skin absorption hazard. Ammonia begins to affect moist skin at exposures greater than 10,000 PPM (1 percent) (mild irritation) and at concentrations great than 30,000 PPM (3 percent) a stinging sensation is observed. Therefore, the general procedure of using Level A equipment at half the IDLH may be unduly conservative for ammonia exposures. For ammonia it may be more appropriate to respond in Level A gear to exposures of half the threshold for skin irritation, or 5,000 PPM.”

The International Institute of Ammonia Refrigeration, or IIAR, Ammonia Safety Data Book adopted the 5,000 PPM standard for setting the maximum limit for using Level B ensembles in ammonia vapor.


The purpose of this paper is to build upon the background used in 1991 that established the 5,000 PPM regulatory interpretation to limit the use of Level B PPE. ASTI has gathered new information, identified new technology, and has additional experience available today to provide an alternative to using the Level A option in levels of ammonia less than 15,000 PPM. We are recommending that OSHA approve a performance-based PPE ensemble created with a combination of protective clothing options to address identified hazards rather than relying exclusively on one of the four EPA created levels of PPE (Level A, B, C, or D).

The hazard analysis on 15,000 PPM of anhydrous ammonia vapor reveals that the inhalation hazard is high, requiring a self-contained breathing apparatus, and the skin damage hazard is low.

The following is a quote from the Industrial Hygiene and Toxicology Volume II, also known as the Patty Handbook, (Frank Patty, Editor, published in 1963, Library of Congress number 58-9220). We believe that OSHA Regional Director Patricia Clark used this information when defining skin damage threat.

“During the approval testing of respiratory protective devices, the author has observed that atmospheres of one percent ammonia are mildly irritant to the moist skin, those of two percent have a more pronounced action, and concentrations of three percent or greater cause a stinging sensation and may produce chemical burns with blistering after a few minutes of exposure.”

The range of concern for ammonia vapor begins with mild irritation at 10,000 PPM and increases to a stinging sensation felt at 30,000 PPM. The decontamination procedure for dealing with a vapor irritation is to aerate the skin and PPE clothing with fresh air from a portable fan.

The following is a summary of the findings that support ASTI’s desire to define a safer PPE alternative to using Level A PPE for working in atmospheres less than 15,000 PPM of anhydrous ammonia vapor.

  • Reducing the time and stress associated with PPE suit-up to enter low-level vapor (under 15,000 PPM of ammonia) will help achieve the response objectives set for engagement in the first 30 minutes of an emergency event. The need for rapid entry rescue, defensive mitigation of the emergency event, and ability to perform reconnaissance to secure the information needed to plan a longer-term response strategy occurs during the first 30 minutes. The overall risks and threats that materialize in the first 30 minutes can be quickly and effectively mitigated to contain and control an emergency event that might otherwise increase to higher concentrations and a greater level of risk and threat to responders and downwind receptors.
  • Level A PPE takes longer to put on than Level B protection. The stresses and medical oversight needed to wear a fully encapsulated suit present life safety challenges for the responder that can be more of a concern than the potential of minor skin irritation from exposure to ammonia vapor under 15,000 PPM.
  • The assumption tat most employers use a Level A response team is incorrect. The trend for employers who work with ammonia has been to drop all emergency response that requires an offensive strategy and, instead, count on public safety to engage hazmat response teams to contain and control an emergency event. Many public agency responders do not have a level A techniciantrained response team immediately available. They may count on a regional response team that takes more than an hour to become operationally available.
  • The life treat and damage froman unattended ammonia emergency can be mitigated if employers are given a more realistic PPE emergency response plan option to engage offensively to contain and control an ammonia release during the first thirty minutes.
  • The use of protective clothing can itself create significant wearer hazards, such as heat stress, physical and psychological stress, and impaired vision, mobility, and communication. The greater the level of chemical protective clothing, the greater the associated risks. For any given situation, equipment and clothing should be selected to provide an adequate level of protection. Overprotection, as well as under-protection, can be hazardous and should be avoided (quoted from the OSHA, Section 7, Chapter #1, Chemical Protective Clothing).


The risk to the responder using Level A ensemble is high, especially when the responder is not comfortable or experienced in emergency circumstances. An article published in Fire Chief magazine (September 2011), revealed that the New York Fire Department made the decision to reduce the level of risk to the responder by creating an optional PPE clothing ensemble rather than mandating Level A fully encapsulated suits to handle all vapor releases of toxic inhalation hazardous vapor. The following is a quote from that article:

“While all of the units are trained for life-safety operations (assessment, packaging and removal) in the Hot Zone, only the Hazmat Technician II units and Hazmat Company 1 are trained for the mitigation of incidents that require vapor protection. Prior to upgrading its chemical protective clothing, or CPC, program, the FDNY issued Level A suits to these units.

New options: the department discovered that for hot-zone responses, fully encapsulated gastight garments, i.e., Level A suits, pose several challenges for the first responder. For instance, such suits trap heat and put the responder at risk for heat injury. Also, vision is obscured when moisture (sweat and respiration) condenses on the inside of the visor. If that wasn’t problem enough, the bulkiness of the suit material required the wearing of oversized boots, and the glove system compromised dexterity. The combination of obscured vision, ill-fitting footwear and decreased dexterity, increased the potential for injury. The packaging and removal of exposed victims are physically demanding tasks that underscore the limitations of using fully encapsulated CPC for hazmat rescues.

It should be noted that the levels of protection (A, B, C and D) outlined in CFR 1910.120 are design standards, not performance standards. In contrast, NFPA standards are performance-based, and they influenced the FDNY’s decision to upgrade its CPC program.

NFPA standards that are applicable to this discussion include the following:

NFPA 1971: Standard on Protective Ensembles for Structural Fire Fighting and Proximity Fire Fighting NFPA 1991: Standard on VaporProtective Ensembles for Hazardous Materials Emergencies

In 2007, NFPA 1994, Standard on Protective Ensembles for First Responders to CBRN Terrorism Incidents, was released. This standard parallels the rescue mission of FDNY’s tiered-response system. Because of this standard, as well as innovations that were occurring at the time, the department further evaluated its hazmat equipment and tactics, with the following objectives: increase department response capabilities with mission-specifi c protection; improve responder safety; and, decrease physical impact on responders.

As a result, two garments were selected for inclusion in the department’s CPC program.

The Trelleborg Trellchem VPS Flash Suit was selected as an upgraded and improved Level A suit for mitigation missions performed by Hazmat Company 1 and Hazmat Technician II units.

Performance improvements include the following:

  • It meets the optional flash-free standard in NFPA 1991;
  • No over-garment yields a 7.3-pound weight savings, which decreases physical strain;
  • Anti-fog hard-impact visor increases safety by improving vision;
  • Improved dexterity
  • Streamlined suit material does not require the use of oversized boots.

The VPS Flash Suit improves safety and decreases the demands placed on hazmat technicians. Mitigation missions often require fine motor skills to make repairs; consequently, improvements in vision and dexterity increase the chance of a successful response using one entry team.

In addition, the Lion MT-94 was selected for rescue missions within the hot zone. Performance improvements compared with the legacy Level A suits include the following: A 3- to 4-minute donning time, which improves the time-to-victim contact; visibility is not an issue due to the non-encapsulating design; a glove system that provides superior dexterity and protection; a substantial reduction in heat stress and physical demand on the first responder; and enhanced garment durability.

The MT-94 is a non-encapsulated, gas/vapor-tight garment that is 13 pounds lighter than the previous Level A suit. The substantial improvements in decreasing heat stress are due in large measure to the garment’s unique material, W.L Gore’s Chempak fabric, that was developed in response to military and first responder requests for a lightweight, highly mobile and durable garment for use in chemical and biological incident response. The fabric sandwiches a protective barrier between two layers of Nomex fabric.

Reduced heat generation was achieved primarily through the dramatically decreased weight of the garment, but also by increasing its flexibility compared with the Level A suit. Heat stress can be reduced further by wetting the garment with water. A combination of conductive and evaporative cooling occurs when the garment is wetted, which decreases the thermal load on the responder. In turn, reducing heat stress and physical exertion decreases air consumption. So, the responder can remain safely in the Hot Zone for longer periods. In training exercises, the department has seen a marked increase in the number of extractions a CPC team can complete before members deplete their air supplies. Moreover, the garment’s improved durability has allowed an expansion of tactical areas of operations to include incidents that were considered too damaging to the Level A suit, e.g., collapsed debris areas. Finally, the MT-94 also can be utilized by a rapid-intervention team to respond to injured members of a mitigation team.”


PPE Parameters: The PPE recommendations made herein are designed to protect the responder (person wearing the gear) within the specifications of the outer protective suit plus a buffer protection provided by clothing worn under the outer suit in case the responder experiences a sudden and unforeseen exposure to threats beyond what was evident when entering the hot zone, e.g., a small aerosol release suddenly becomes a large aerosol release (greater than 3 cubic feet) or suit damage results in a vapor leak through the outer suit.

The Incident Commander and responders must be trained technicians to engage any offensive operation within the hot zone. They must have a full understanding of the hazards, risks, and threats, and they must be equipped with proper monitoring equipment to determine that entry into the hot zone is safe within the scope of the adopted PPE emergency response SOP(s). The hot zone hazards, risks, and threats may be pre-defined in a Hazard Zone Checklist that is included in the emergency plan, or within an ICS 215A form and/or an ICS 208 form that defines hazards and mitigations for the hazards within the hot zone before entry is allowed by the responders.

Hazard Zone Disclaimer: The PPE recommendations defined within this document are not intended to cover a circumstance in which the responder is entering a hot zone that involves an out-of-control aerosol release that is developing into a dense gas cloud (greater than three cubic feet) and is moving towards a source of ignition, or spreading at a rate that will place responder(s) at an uncertain level of risk. An out-of-control aerosol stream may have the potential to transition into a highly flammable and extremely cold environment within several minutes. This would require the highest level of PPE with a fully encapsulated entry suit, flash-fire protection, and thermal insulated clothing and gloves that resist damage at temperatures as low as -80°F. Entry into an atmosphere that threatens to transition to this type of circumstance is not within the scope of the PPE recommendations provided herein.

Identification of the hazards or suspected hazards: ASTI recommends that a Pre-Emergency Readiness Checklist and a Hazard Zone Checklist (provided as an appendix to this document) be created for every facility using anhydrous ammonia. This information helps define the level of PPE engagement using a faster and more accurate hazard analysis. The pre-arranged hazard analysis provided within the Pre-Emergency and Hazard Zone checklists defines the hazards, risks, and threats, as well as the defensive measures used to reduce the impact of the ammonia release. The Hazard Zone details are put into place by a Command Team made up of an Incident Commander, Lead Responder, Evacuation Group Supervisor, and notification Unit Leader. An Incident Commander may appoint a Plans Section Chief or a Safety officer to develop a Situation Status Report and advanced hazard analysis for engagement beyond the first thirty minutes of emergency response engagement.

There are seven hazard scenarios that the SOP for entering any atmosphere above PEL (Permissible Exposure Level), Isolation Zone, or Hot Zone must address:

  • Defensive action in atmospheres less than IDLH and greater than PEL: Evaluate and prepare for the hazards, risks, and threats associated with entry into the hazard zone by reviewing the Pre-Emergency Readiness checklist and/or the Hazard Zone checklist provided in the emergency plan, or develop an ICS 215A hazard analysis.
  • Engaging in command and support functions: Those conducting command assignments on the outer perimeter of the Isolation Zone or Protective Action Zone may experience an occasional shift of vapor and may need an escape hood or APR. Levels of ammonia may exceed the IDLH temporarily. The same is true for those performing decontamination on a person who has aerosol or liquid burns.
  • Those trapped in an ammonia contaminated environment may also use an escape hood to move through ammonia vapor that exceeds the IDLH limits. ASTI recommends that a person should not escape through a dense gas cloud of ammonia without the highest level of respiratory protection.
  • Incidental control of an emergency event as defined by OSHA limits: The definition of Incidental control is provided in the Definitions section of this document. UÊEntry into the hot zone for levels of risk above the IDLH: The Incident Commander and entry team must be technician trained. They will conduct a pre-entry briefing to assure that the Incident Action Plan (IAP) and Safety Plan address the acknowledged hazards and risks. The Hazard Zone Checklist, ICS 215A, and/or ICS 208 may be used to support the IAP. The entry team must be supported by back-up, decontamination set-up, and rehab support. On-air time must be monitored by the IC or Safety officer. UÊEntry to perform reconnaissance and hazard assessment: Responders may not have all the evidence needed to properly judge the hot zone and will need to enter to assess the conditions before initiating containment and control measures, other than incidental control on the way to and from the Hot Zone. Entry into IDLH conditions requires the same level of oversight as described in the previous bullet statement.
  • Entry for rapid extrication “grab and go” rescue: Rescuing a person who is down within the hot zone is the most challenging response protocol for the employer to create. The first steps of the rescue will require a hazard assessment. Those participating in rapid extrication rescue must be trained on how to perform the rescue evolution. The options for rescue include: defensive measures (reduce risk by managing the release using mitigations), placement of a portable fan to move the ammonia vapor away from the rescue victim, entry to supply the victim with PPE to survive the exposure, and entry to move the victim from the hot zone.


Ammonia presents a high level of respiratory threat and a reduced level of concern for skin damage, especially at exposure levels of 10,000 PPM or less (based upon the conditions defined in PPE Parameters and limitations prescribed by ASTI and described within this document). The OSHA standard is clear that the transition from APR (Air Purifying Respiratory) to SCBA occurs at the IDLH of 300 PPM.

Inhalation Hazard: The hazards of vapor exposure of 15,000 PPM or less represent a respiratory threat that can be mitigated with an APR at levels below 300 PPM. A SelfContained Breathing Apparatus is required at levels above the IDLH.

Ingestion Hazard: The full-face mask APR or SCBA will provide adequate protection from the threat of ingesting ammonia. There will be no other details provided to address ingestion of ammonia because the PPE SOP begins with the mandatory use of an APR or SCBA to mitigate this threat.

Skin Absorption: Exposure to ammonia vapor has been characterized by OSHA Region II Director Patricia Clark as being “mild irritation” at 10,000 PPM and a “stinging sensation” at 30,000 PPM. ASTI has conducted live ammonia PPE testing that confirms that assessment. ASTI conducted a data search for medical reports and specific medical findings regarding skin tissue burns associated with exposure to anhydrous ammonia vapor. The conclusions of the medical advisors1 who were consulted reveal that there are little or no medical findings in recent history that provide medical evidence of serious injury due to exposure to ammonia vapor in atmospheres less than 15,000 PPM. There is plenty of medical evidence of inhalation injury and thermal, chemical burns associated with exposure to aerosol stream and liquid ammonia exposure.

The alkaline burns associated with ammonia occur when anhydrous ammonia mixes with water, as in contact with body fluids (eyes and respiratory track). When significant amounts of vapor mix with body fluids irritation begins to develop starting with itching eyes and a tickling sensation at 150 to 700 PPM, progressing to airway closure due to the irritation created in the esophageal airway at 1500 to 2700 PPM.

The pH of ammonia becomes a factor for skin irritation when anhydrous ammonia mixes with water. A weak alkaline is developed (maximum of 11.2 pH). Direct exposure to skin moisture , usually body sweat in the armpits or groin, produces mild skin irritation at 1 percent (10,000 PPM). Skin irritation at 3 percent (30,000 PPM) creates a cold, stinging sensation. Skin exposure can be decontaminated by an air-driven portable fan. When exposed to aerosol dense gas or liquid ammonia, the victim should be showered with water for at least 15 minutes.


  • 1975 survival of Mickey Johnson and her son who were caught in an ammonia cloud on a Houston freeway: Mickey experienced no skin injury but did experience significant respiratory damage. Her 2-year-old son experienced no significant long-term injury because Mickey covered him with a coat that shielded him from dense gas exposure.
  • 2010 Minot, North Dakota, train derailment: Approximately 1 million pounds of ammonia traveled through Minot. Exposures within some of the homes exceeded 1,000 PPM. There was no evidence of ammonia skin burns.
  • 2012 survival of Jose Mata in Yuma, Arizona: He was thrown to the ground when a condenser failed due to over-pressure that instantaneously released a large volume of ammonia. The concussion of the mechanical explosion threw Jose on his back and he was completely covered in an aerosol-dense gas cloud. He held his breath, closed his eyes, and ran out of the ammonia cloud. He suffered thermal burns and chemical burns to his lower torso because his clothing (pants and boots) were left on during and after initial decontamination. The high pH of the aqua-ammonia solution caused serious chemical burns. Jose’s face and upper torso did not show any evidence of vapor burn.
  • In February of 2012 the fire department in Yuma, Arizona, worked with ASTI to test the protection of firefighter turnout gear while performing a tarp and cover evolution over a high-pressure/high-volume aerosol ammonia release (150 psi through a 3/4” outlet). Two firefighters got too close to the aerosol release and were caught in a visible dense gas cloud. The ammonia vapor (at about 30,000 PPM) entered the legs of their turnout pants. They immediately went to the decontamination fan for decontamination. The vapor burning sensation was mitigated within several minutes and there was no evidence of skin irritation. The firefighters were wearing knee-length shorts under their turnouts, so the irritation factor was more significant than if they had been wearing long underwear or cotton pants.


On three different occasions, ASTI has tested exposure levels when wearing overalls, CBRN first responder overalls, fi re turnouts, Level B (un-taped), and Level B (taped). The tests were conducted inside training buildings at the Military Operations on Urban Terrain (MOUT) training facility at Fort Ord in California. OSHA and EPA officials witnessed the tests. ASTI team members, the Salinas Fire Department Hazmat Team, and the 95th Civil Support Team from Hayward, California, participated in the ammonia vapor PPE evaluations. The results of the testing consistently showed that exposure within the 1 percent to 3 percent mixture is consistent with Ms. Clark’s letter regarding skin exposure.

The test procedure was conducted within an enclosed 20’ x 30’ room with an 8’ ceiling. Small amounts of liquid ammonia (approximately 2 cups per spill) were dropped on the cement floor. The ammonia vapor evaporated into a small cloud and then dispersed into the room, slowly building up the ammonia vapor concentrations. Four entry team responders were dressed in different levels of PPE:

  1. CBRN protective overalls with charcoal-filtering protective layer; the entry person wore shorts;
  2. Nomex overalls with cotton blend pants and shirt under the overall;
  3. Fire turnouts meeting NFPA standards for fire protection;
  4. Level B over-suit with no taping of the arms, legs, and face mask;
  5. Level B oversuit taped at the arms, legs, and zipper flap (upper torso). The face mask seal was a built-in gasket connection (available with some suits) and/or a Nomex hood that overlaps the face mask.

The room was monitored by two handheld ammonia monitors and Honeywell ammonia sensors strategically located within the room. The concentration of ammonia vapor was monitored as those who were exposed walked about the room to simulate working in ammonia vapor conditions.

The ASTI findings are categorized for the various levels of skin protection as follows:

  • CBRN Overalls (under clothing-shorts with unprotected legs from the knees down): Those who wore overalls with no second layer of clothing (long-legged pants) and open cuffs were the first to experience skin irritation on the legs and crotch area at approximately 8,000 to 10,000 PPM.
  • Overalls with cotton pants and shirt under the overalls: skin irritation began with a sense of cold and slight stinging sensation at approximately 17,000 PPM.
  • Fire Tournouts: at 20,000 PPM minor skin irritation in moist areas of the body was felt.
  • Level B Un-Taped: resulted in minor irritation at approximately 25,000 PPM.
  • Level B Taped: experienced no discomfort at levels above 25,000 PPM.

In all cases, skin irritation was mitigated by decontamination with a portable fan.

Responders must comply with OSHA requirements for PPE response and be properly equipped with appropriate respirators. The hot zone environment, where entry takes place, must be monitored with handheld or fixed system monitoring that reads the constant exposure levels. Decontamination, medical readiness, safety oversight, and other applicable OSHA requirements must be in place as per the emergency response plan SOP. ASTI recommends that OSHA approve the following criteria for working within atmospheres of ammonia vapor:

  • Maximum of 5,000 PPM exposure within a Hot Zone while wearing cotton or fire-resistant overalls over long underwear or clothing (long-sleeved shirt and full-length pants);
  • Maximum of 10,000 PPM exposure with Level B over-suit un-taped;
  • Maximum of 10,000 PPM exposure with fire turnouts meeting NFPA specifi cation;
  • Maximum of 15,000 PPM exposure with Level B over-suit with chemical resistant tape-seal at all suit openings.

Justification for the exposure limits: Exposure to levels above 30,000 PPM for any of the PPE ensembles described above is unlikely. The entry team is prohibited from entering if an aerosol/dense gas cloud is forming. The emergency responder will be backed up with a buddy who can assist the entry team in reaching decontamination AND the undergarments used for the PPE ensemble (should a tear or other failure allow ammonia vapor to enter the suit) will be adequate to protect the responder to the point of decontamination with little or no skin irritation beyond slight discomfort. The 15,000 PPM limit does not present as big a concern for skin irritation as it does for breathing (SCBA). The increased vision, mobility, and physical comfort afforded by the ASTI-recommended levels of PPE will result in a safer overall response than if responders wear Level A ensembles (with the potential of heat, tripping, and stress-related problems).


The future of creating a more appropriate level of PPE for defined entry into hazard zones involving less than 15,000 PPM of ammonia vapor will require clarification of the various code interpretations and verbiage by OSHA.

The following OSHA information must be clarified by code enforcement leadership within OSHA to assure that an employer-developed SOP using the logic presented in the document is appropriately designed.

There is inconsistency in the parameters associated for Level B PPE protection written in Section VII, Chapter 1 of the OSHA Technical Manual and the 1910.120 Appendix B definition of Level B protection.

Section VII states “no protection against chemical vapors or gases,” and then later states that “primary hazards associated with site entry are from liquid and not vapor contact.”

OSHA 1910.120 Appendix B regarding Level B states “The highest level of respiratory protection is necessary but a lesser level of skin protection is needed.” Both quotes are cited below:


LEVEL B: Liquid splash-protective suit (meets NFPA 1992); pressuredemand, full-face piece SCBA, inner chemical-resistant gloves, chemicalresistant safety boots, two-way radio communications

Hard hat. OPTIONAL: Cooling system, outer gloves

Protection Provided: Provides same level of respiratory protection as Level A, but less skin protection. Liquid splash protection, but no protection against chemical vapors or gases.

Used When: The chemical(s) have been identified but do not require a high level of skin protection. Initial site surveys are required until higher levels of hazards are identifi ed. The primary hazards associated with site entry are from liquid and not vapor contact.

Limitations: Protective clothing items must resist penetration by the chemicals or mixtures present. Ensemble items must allow integration without loss of performance.


II. Level B – The highest level of respiratory protection is necessary but a lesser level of skin protection is needed.

The following constitute Level B equipment; it may be used as appropriate.

  1. Positive pressure, full-facepiece self-contained breathing apparatus (SCBA), or positive pressure supplied air respirator with escape SCBA (NIOSH approved).
  2. Hooded chemical-resistant clothing (overalls and long-sleeved jacket; coveralls; one or two-piece chemical-splash suit; disposable chemical-resistant overalls).
  3. Coveralls. (1)
  4. Gloves, outer, chemical-resistant.
  5. Gloves, inner, chemical-resistant.
  6. Boots, outer, chemical-resistant steel toe and shank.
  7. Boot-covers, outer, chemicalresistant (disposable). (1)
  8. Hard hat. (1)
  9. [Reserved]
  10. Face shield. (1)

Footnote (1) Optional, as applicable

There is no doubt that Level B PPE protection offers some protection from ammonia vapor. OSHA Regional Director Patricia Clark made this fact clear in her Letter of Interpretation for Level B use on ammonia emergencies.

The threats associated with an ammonia vapor release (under 15,000 PPM) are predominantly an inhalation threat rather than a skin damage concern. The utilization of Level B PPE and, to a lesser degree, fi re turnouts or overalls and self-contained breathing apparatus is a reasonable alternative to Level A fully encapsulated suits when working exclusively in ammonia vapor for short durations of time (under 10 to 15 minutes).

The appropriate resolution to this code-related conflict is to use the most specific regulatory requirement, which would be the 1910.120 Appendix B wording.

Further code-related support that is used to focus the use of Level A and B protection is provided with the following Federal OSHA 29 CFR code citations:

1910.120(g)(3)(iv): Totally-encapsulating chemical protective suits (protection equivalent to Level A protection as recommended in Appendix B) shall be used in conditions where skin absorption of a hazardous substance may result in a substantial possibility of immediate death, immediate serious illness or injury, or impair the ability to escape.

1910.120(g)(3)(v): The level of protection provided by PPE selection shall be increased when additional information or site conditions show that increased protection is necessary to reduce employee exposures below permissible exposure limits and published exposure levels for hazardous substances and health hazards (see Appendix B for guidance on selecting PPE ensembles).

NOTE TO PARAGRAPH (g)(3): The level of employee protection provided may be decreased when additional information or site conditions show that decreased protection will not result in hazardous exposures to employees.

1910.120 Appendix B: As an aid in selecting suitable chemical protective clothing, it should be noted that the National Fire Protection Association (NFPA) has developed standards on chemical protective clothing. The standards that have been adopted include:

NFPA 1991 – Standard on VaporProtective Suits for Hazardous Chemical Emergencies (EPA Level A Protective Clothing)

NFPA 1992 – Standard on Liquid Splash-Protective Suits for Hazardous Chemical Emergencies (EPA Level B Protective Clothing)

NFPA 1993 – Standard on Liquid Splash-Protective Suits for Nonemergency, Non-fl ammable Hazardous Chemical Situations (EPA Level B Protective Clothing)

These standards apply documentation and performance requirements to the manufacture of chemical protective suits. Chemical protective suits meeting these requirements are labeled as compliant with the appropriate standard. It is recommended that chemical protective suits that meet these standards be used.


PPE Protection:

The amount of protection offered by a particular type of PPE is material and hazard-specific. Certain types of PPE will protect well against some hazards and poorly, or not at all, against others. Other factors in the selection process include matching the PPE to the employer’s work requirements and task-specific conditions. The durability of the PPE materials, as well as its performance in extreme heat or cold, must also be considered when: Climbing ladders or entering confined space. Jumping, reaching, or extending beyond routine walking and arm motions. Permeation data should include the following:

  • Chemical name;
  • Breakthrough rate( shows the rate soon the chemical permeates);
  • Permeation rate (shows hor that the chemical comes through);
  • System sensitivity(allows comparison of test results from different laboratories);
  • A citation that the data was obtained in accordance with ASTM Standard Test Method F739-85. If no data are provided or if the data lack any one of the above items, the manufacturer should be asked to supply the missing data. Manufacturers that provide only numerical or qualitative ratings must support their recommendations with complete test data.

Liquid penetration data should include a pass or fail determination for each chemical listed, and a citation that testing was conducted in accordance with ASTM Standard Test Method F903-86. Protective suits that are certified to NFPA 1991 or NFPA 1992 will meet all of the above requirements.

Particulate penetration data should show some measure of material efficiency in preventing particulate penetration in terms of particulate type or size and percentage held out. Unfortunately, no standard tests are available in this area and end users may have little basis for company products.

Suit materials which show no breakthrough or no penetration to a large number of chemicals are likely to have a broad range of chemical resistance. Breakthrough times greater than one hour are usually considered to be an indication of acceptable performance. Manufacturers should provide data on the ASTM Standard Guide F1001-86 chemicals. Manufacturers should also provide test data on other chemicals as well. If there are specifi c chemicals within your operating area that have not been tested, ask the manufacturer for test data on these chemicals.


PPE selection based upon site hazards: Pre-Entry Hazard Analysis to enter an atmosphere above the PEL and for entry into a hot zone.

Selection of the proper PPE ensemble to meet the hazards, risks, and threats existing in the hot zone

Buddy system and PPE readiness review of entry Incident Action Plan objectives, safety plan, and a review of emergency communications. The physical and mental readiness, as well as hydration, of the entry team to enter the hot zone are also priorities.

IC approval to enter the hot zone with an Incident Action Plan describing the entry objective(s) designed to be accomplished within 10 minutes of entry time (or in a timeframe consistent with air bottle time and personnel readiness training limits); and IC or Safety Offi cer monitoring of on-air time while in the hot zone, and clarifi cation of the Safety Plan to include a review of the hand signals and other means of communications prior to entry


Visual, verbal, and/or tag line communications between entry team, back-up, and the Incident Commander,

Decon, medical evaluation, and rehab (hydration) upon leaving the Hot Zone.

Pre- and post-entry briefing: Prior to entry into the Hot Zone, the Incident Commander must be assured that the Entry Team is briefed as defined in the PPE standard of operation.

Work mission duration: The work mission will be defi ned within an Incident Action Plan approved for implementation by the Incident Commander. The entry time will be monitored, especially for on-air time (SCBA). The maximum working time within the Hot Zone must be 15 minutes or less. The work mission will be described, assuring that the dexterity and construction of the PPE entry suit is within safe standards to minimize damage to the suit.

PPE Procedures not discussed in this document: The code requirements that govern the use of PPE during a hazmat emergency are clearly defi ned within the 29 CFR 1910.120 requirements, and within the state-adopted safety requirements that fulfill the OSHA requirements in 1910.120. The following is a list of the subject matter NOT specifi cally covered within this document:

  • PPe maintenance and storage;
  • PPE decontamination and disposal;
  • PPE training and proper fitting;
  • PPE donning and doffing procedures;
  • PPE inspection procedures;
  • Evaluation of program effectiveness;
  • Limitation due to external or medical conditions;
  • 1910.134 Respiratory program requirements


The evidence provided within this document clearly supports the ASTI recommendation to provide more alternatives for PPE choice when working in lower than 15,000 PPM of ammonia vapor (with no aerosol cloud greater than 3 cubic feet within the entry hot zone). The criteria described within this document define the conditions by which the PPE judgment can be made by the Incident Commander to vary from the existing standard of wearing Level A fully encapsulated entry suits for ANY release that exceeds 5,000 PPM.

ASTI has provided evidence and related experiences that show that alternative levels of PPE (other than Level A) provide protection to the responder and an overall improvement of the health and safety concerns, especially when the risks and threats of wearing Level A ensembles are considered.

The improved timeframe and availability of alternative PPE choices described within this document will provide first responders with the ability to engage rapid entry rescue, a defensive mitigation strategy, and control small releases before they have time to develop into major life threatening events.


ASTI conducts a 32-hour course on advanced subject matter related to managing ammonia emergencies. In October 2010 and November 2011, the subject of personal protective equipment was evaluated by testimony from experts from OSHA, Department of Homeland Security, Center for Toxicology and Environmental Health, and EPA. Kent Anderson, Vice Chair of the ASTI Board of Directors and President Emeritus of the International Institute of Ammonia Refrigeration (, played a big role in bringing these players together and has made connections to pave the way for ASTI to make the recommendations within this document. The following is a list of those who participated in the PPE evaluation conducted at the 32-Hour course. They suggested that ASTI create a technical document that would be peer reviewed to defi ne the PPE recommendations contained herein. This document begins that process. 

The documentation and planning forms originally presented with this technical paper and referenced in this issue of the Condenser are not reprinted here in the interest of space. To obtain these forms and learn more about the information discussed in this Technical Paper, contact Gary Smith at

Todd Jordon, MSPH, CIH, Director of USDOL/OSHA Health Response Team, and Brian T. Liddell, MSPH, CIH, Chemical Engineer, Health Response Team, OSHA Salt Lake Technical Center, 8660 S. Sandy Parkway, Sandy, UT 84070,

Ron Hill, CEO, Hill Brothers Chemical, 1675 North Main St., Orange, California 92867, ronhill@

Martin Wehner, President, Airgas Specialty Products, 2530 Sever Road, Suite 300 Lawrenceville, GA,

Troy Baker, Industrial Refrigeration Division Manager, Honeywell Analytics, troy.baker@

Fredrick W. Malaby, C.I.H., C.S.P. Industrial Hygienist, OSHA , JFK Building, Room E-340, Boston, MA 02203,

Glenn E Lamson, CIH, Industrial Hygienist, Salt Lake Technical Center, 8660 S. Sandy Parkway, Sandy, UT,

Jedd Hill, Industrial Hygienist, Salt Lake Technical Center, 8660 S. Sandy Parkway, Sandy, UT, hill.

Dr. Paul Nony, Senior Toxicologist, Center for Toxicology and Environmental Health, LLC 5120 North Shore Drive, North Little Rock, AR 72118, pnony@

Mike Doering, Cal/OSHA Div. of Occupational Safety & Health, Torrance, CA 90502,

Robert Cole, Division Chief (retired), Chevron Refi nery, Pascagoula, MS, and ASTI Master Instructor and Board member,

Captain Rick Williams, Salinas Fire Department, 20331 Via Espana, Salinas, CA 93908, Rickyw@