Background Information

In July 1997, the Montgomery County Fire and Rescue Service (MCFRS) sent a letter to the United States Army Soldier and Biological Chemical Command (SBCCOM), Aberdeen Proving Ground, Maryland. requesting that they conduct tests to determine how protective firefighters' PPE would be against a chemical agent (simulant) vapor challenge.

After several meetings and telephone conversations, SBCCOM's Chemical Weapons Improved Response Program (CW IRP) embraced the project and provided ongoing input and assistance. Tests began in January 1998. These initial tests lasted over a period of approximately eight months. Initial vapor testing was done in Aberdeen, Maryland and the verification tests were conducted at a research facility in Canada.

Two firefighters were used in each of these series of tests. Passive sampling devices (PSD) were strategically located on different areas of the skin of each firefighter to measure the uptake of a harmless chemical agent simulant. After each test, the PSDs were removed and their contents were collected and later analyzed. Using the Body Region Hazard Analysis algorithm developed by scientists from SBCCOM and the Army's Center for Health Promotion and Preventive Medicine, the average percutaneous (skin) protection factor could be calculated.

All the tests were conducted in 30-minute periods. The initial series of tests involved members of the MCFRS. These members also participated in the first four verification tests conducted in Canada. Firefighters wore new, "off-the-shelf," personal protective coats, pants, boots, gloves, and protective hood. After their initial use, the personal protective clothing were commercially cleaned for later tests.

Each of these tests required the two firefighters to perform a specific number of activities. These activities were designed to reflect the kinds of activities firefighters would likely perform if engaged in a rescue operation. Some of the activities were climbing a ladder, dragging and carry a 160-pound dummy, reaching and resting. Theses activities challenged the firefighters' range of motion and also provided opportunities for the simulant to enter the clothing through openings in the protective clothing.

The initial series of tests provided the percutaneous (through the skin) protection factors for different arrangements of personal protective ensembles (Table 1). These protection factors (PF) provide an indication of how protective that particular ensemble would be against exposure to a chemical agent vapor. For example, a firefighter wearing personal protective equipment (PF=10) and using positive pressure SCBA enters a contaminated building with a constant concentration of 40 mg/m3 sarin vapor and remains for one minute, he or she would actually experience the overall skin exposure effects of a concentration of one-tenth that value or 4 mg-min/m3. It is important to note that the actual individual dose received by each exposed person would likely vary based on factors such as respiratory capacity and rate.

Table 1 Overall Protection Factors (increase in skin protection compared to unprotected skin) PPE "System" *PF (average) Standard PPE 10 Operational (Self) Taping 15 Trash Bag (Top) 20 Double Trash Bag 30 Tyvek F Suit 55 Tyvek F Suit Under Standard PPE 100 *rounded off values

Baltimore County Fire Department personnel participated in subsequent tests. They used "off-the-rack" PPE that had already been in use for varying periods. Additionally, they were of a different material than that used during the initial tests.

The data indicated that the "used protective clothing" resulted in higher protection factors than the new protective clothing. While I am unaware of any scientific data to support the difference, I suspect that it is due to carbon impregnation in the fabric from repeated fire exposures, or physical changes in the fabric resulting from washing, or both.

Terminology

To facilitate understanding, some terms are described below. Readers should review other references for more detailed explanations and examples

LCt50

What does the expression LCt50 mean? Literally, it means the lethal concentration of a chemical agent exposure by inhalation to kill about 50% of unprotected people.

L = lethal
C = concentration of vapor expressed in mg/m3
T = exposure time expressed in minutes
50 = percent of people would likely die from that exposure

If 100 people were in a room and there was a uniform concentration of a chemical agent (vapor) such that breathing it for one minute would probably kill about 50% of them, that would be the LCt50 for that agent. One reference indicates that the "high-end" LCt50 for sarin is 100 mg-min/m3. So, if the unprotected people were to breath the sarin vapor concentration for one minute, about 50% of them would most likely die. For a concentration of 25 mg/m3, the people would have to inhale that concentration for four minutes (25 x 4) to kill about 50% of them. Typically, Ct products having the same value provide similar physiological effects in exposed people. Examples are provided in Table 2.

Table 2 Examples of Ct Products for Lethal exposure to Sarin Vapor (100 mg-min/m3) C (mg/m3) 100 50 25 10 5 t (min) 1 2 4 10 20 Ct (mg-min/m3) 100 100 100 100 100

ICt50

There is another expression, , used to indicate the concentration for a specific time to incapacitate at least 50% of the people exposed. Depending on the particular chemical agent, the difference between lethality and incapacitation might be small.

LCt50 for Sarin by Percutanenous (through the skin) Exposure

If 100 firefighters were using SCBA without personal protective clothing were exposed to a uniform concentration of 15,000 mg/m3 of sarin vapor for one minute, about 50% of them probably would die. This is 150 times the concentration necessary to kill 50% of the victims by inhalation for the same period of exposure.

P/I Effective Dose Ratio

This is an expression that I created to express the ratio of the percutaneous exposure effective dose of a specific chemical agent to the inhalation exposure effective dose of the same chemical agent. This ratio indicates that a higher vapor concentration is needed for a percutaneous exposure compared to an inhalation exposure to the same chemical agent to achieve similar physiological effects. Chemical agents have different percutaneous-to-inhalation (P/I) effective dose ratios (Table 3).

Table 3 *P/I Effective Dose Ratios for Chemical Agents Agent Tabun Sarin Soman Lewisite VX Mustard Symbol GA GB GD L VX H *P 30,000 15,000 10,000 >100,000 360 10,000 *I 135 100 70 1,500 30 1,500 P/I 222 150 143 67 12 7 *Estimated

To further emphasize the significance of the P/I ratios, consider the following example: If unprotected victims were exposed to a 4 mg/m3 concentration of sarin vapor for five minutes, the resulting exposure would be 20 mg-min/m3. Theoretically, if firefighters, just using SCBA without personal protective clothing, entered the contaminated area with the same consistent sarin vapor concentration as the unprotective victims, they could remain in that environment 150 times longer or 750 minutes (12.5 hours) before they would receive similar effects as the unprotected victims. Expressed another way, these firefighters could be exposed to 150 times the inhalation concentration of the unprotected victims for the same period of exposure to experience similar physiological effects. Obviously, firefighters would not attempt rescue without wearing all of their PPE. The purpose of this example was to illustrate the dramatic difference between percutaneous and inhalation cts resulting in similar physiological effects.

Summary of important observations

• Unprotected victims who are still alive should be rescued without appreciable delay.
• The firefighter's SCBA (positive pressure) provide an inhalation protection factor of at least 10,000.
• The firefighter's personal protective equipment (PPE) with and without taping, provide skin protection factors of about 15-20 and 10, respectively.
• If unprotected, alive people are visible in the contaminated building, firefighters wearing PPE can quickly rescue them with little risk.

General Guidelines Developed by the U.S. Army SBCCOM

In August 1999, SBCCOM published a 65-page report titled, Guidelines for Incident Commander's Use of Firefighter Protective Ensemble (FFPE) with Self-Contained Breathing Apparatus (SCBA) for Rescue Operations During a Terrorist Chemical Agent Incident. According to the report, standard turnout gear with SCBA provides a first responder with sufficient protection from nerve agent vapor hazards inside interior or downwind area of the hot zone to allow 30 minutes rescue time for known live victims.

Self-taped turnout gear with SCBA provides sufficient protection in an unknown nerve agent environment for a 3-minute reconnaissance to search for living victims (or a 2-minute reconnaissance if HD is suspected). Operating under theses guidelines is not risk-free. Unnecessary exposures should always be avoided. However, when the situation dictates an immediate reaction, these guidelines will help keep risks manageable.

This report does provide substantial information to help the Incident Commander decide whether or not to send firefighters who are properly wearing and using their PPE to quickly rescue casualties who are alive inside a building contaminated with a nerve agent such as sarin. Obviously, the Incident Commander will not likely know at the outset of on scene operations what type of chemical had been released.

Montgomery County Guidelines

The knowledge gained by the MCFRS while working with scientists at SBCCOM, allowed us to develop a quick reference in December 1998. Presently, we are in the process of updating this reference. Some of the key points noted in our guidelines are listed below:

• If the number of live victims exposed to and impaired by a chemical agent(s) exceeds the availability of personnel in level A protection to rescue in a timely manner, then the Incident Commander must consider the use of other acceptable personal protective ensembles. The purpose of this Quick Reference is to give first responders guidelines to help them develop an action plan to safely and effectively rescue live victims during these extraordinary and extreme conditions. Saving live victims is the rescue mission, while minimizing risk of harm to the rescuers.

• Note: Unless the chemical agent(s) is (are) identified by class or name, first responders must gather information about the incident based on: signs and symptoms of casualties, comments from casualties and onlookers, site specific information, their own observations and reconnaissance, and information available through intelligence provided by law enforcement officers. Always assume that mustard agent is present, until otherwise ruled out.

• Key Factors and Steps to Help Decide Whether Rescue is a "Go" or a "No Go" Situation:
  • Weather Conditions: Consider the impact of wind direction and speed, temperature and humidity, and precipitation on the behavior and spread of the chemical agent(s) and on emergency operations. Use on-scene weather monitoring equipment if available.

  • Scene Hazard Assessment: Avoid "tunnel vision." Don't just assume chemical-related hazards. Also consider the possible presence of biological agents, radiological materials, and/or explosive devices.

  • Reconnaissance (Recon): Conduct Recon to determine if live victims are still in the area of the chemical agent release. Unless wearing level A protection, just view the contaminated area through a closed window, an entrance doorway, or other reasonably safe location, to gather victim information. The Recon team must wear at least their protective clothing, with openings taped, and using SCBA.

  • Victim Information:
    • Location: Are casualties visible near an entrance? Are they in the line-of-sight? Can they be heard? Estimate how long it would take to reach and remove them.
    • Number: If there are enough hazmat team personnel in Level A protective suits available to rescue live victims in a timely manner, use them. Otherwise, consider using personnel who are wearing an acceptable protective clothing alternative, with SCBA, as approved by the Incident Commander.

  • Rescue and Standby Teams: Select at least two personnel per team with appropriate personal protection.

  • Chemical Agent Hazard Reduction: Consider use of positive pressure ventilation (PPV) fans (electric preferred) or other fans to reduce or redirect vapor or aerosol concentration. Be sure that use of these fans will not spread chemical agent to endanger other people. If fans are acceptable, they should be placed in service while rescuers are donning their protective ensemble.

  • Review Information about Chemical Warfare Agents (CWA): Remember, all chemical warfare agents are heavier than air, except for HCN. The higher the vapor pressure of a CWA, the higher its rate of evaporation (volatility). Temperature and humidity can affect CWA properties and exposure risk.

  • SCBA (positive pressure): SCBA must be used for all rescue missions. SCBA provide an inhalation Protection Factor (PF) of 10,000. This is excellent respiratory protection.

  • Personal Protective Equipment (PPE): While tests indicated that the Tyvek F suit worn under personal protective clothing provided the highest skin protection factor of the different ensembles tested, the Incident Commander may allow the use of Firefighter's PPE with or without taping of openings and closures.

  • Rescue Team Exposure Time: Limit the initial exposure time to 2-3 minutes. No entry team will re-enter the contaminated area unless authorized and extreme circumstances clearly warrant doing so. Based on chemical warfare agent(s) released, the quantity, its properties, the circumstances surrounding its release, and vapor suppression measures used, the Incident Commander may allow the rescue personnel to operate in the contaminated area for a longer period.

  • Caution: Because concentrations of the chemical agent released in a building could result in different concentrations in the rooms and corridors, victims should be removed through doors or windows that lead directly to the outside. If this is not possible, the rescuers should consider the use of suitable escape masks or chemical masks by victims who must leave through other rooms and corridors to reach the outside.

    Caution: When deciding which way to remove victims, remember that the chemical agent released is likely to be heavier then air. So, victims at ground level should be removed through a window or door that leads directly to the outside. When evacuating upper floors, consider removing victims through upper floor windows or by roof, using ground or aerial ladders.

    Caution: Face Piece Removal. After exiting the rescue area, rescuers must continue using their SCBA to prevent respiratory harm from "off-gassing" of chemical agent until their decontamination is complete. The regulator and face piece must be the last items removed.

  • Emergency Decontamination: Unless delay would compromise rescue, set up decontamination area before entry is made, locate setup as close as practicable, and monitor operations. Rescuers must remove their protective clothing before removing their regulator and face piece to avoid breathing any vapors possibly trapped in their clothing. Use chemical agent monitors to rule out the presence of chemical agent vapors.

  • Medical Monitoring: Check vital signs and ECG. Check again for chemical agent signs and symptoms.

  • Rehabilitation (REHAB): Provide rest and re-hydration. Re-check vital signs as necessary.

Closing Comments

The SBCCOM report, Guidelines for Incident Commander's Use of Firefighter Protective Ensemble (FFPE) with Self-Contained Breathing Apparatus (SCBA) for Rescue Operations During a Terrorist Chemical Agent Incident is an excellent resource to command officers and other emergency services personnel. It provides information to help first responders formulate a "quick rescue" plan.

I am confident that we can quickly rescue victims who are alive from a contaminated building while using PPE and following acceptable guidelines. To accomplish this crucial objective with low risk requires developing an action plan that includes many of the factors discussed previously and in the SBCCOM report. I recommend that the readers view this topic with an open mind. Questions should not go unanswered. Discuss this timely matter with first responders in other fire departments. There are different approaches. The MCFRS guide is simply one approach. Make your decision based on facts, not lack of them. Obviously, it is much better for emergency responders to decide now how they would manage the quick rescue of victims, than to wait until the issue presents itself in a real terrorist chemical agent event.

Related:

• Weapons Of Mass Destruction Archives
  

About the Author - Ted Jarboe, M.S., C.E.M. Ted Jarboe is a Deputy Chief with the Montgomery County (MD) Fire and Rescue Service. He is the County’s Fire Marshal and also heads the Bureau of Life Safety Services. Jarboe has been a member of many local, state and federal programs involved with studying and training for weapons weapons of mass destruction (WMD) incidents. He has tested and trained with a wide range of equipment used in such incidents. In January 2000, he designed and created a website titled WMD First Responders www.wmdfirstresponders.com. Ted Jarboe has 38 years of career service.