By WILLIAM F. CANDY
One of the documented firefighter concerns is the possibility of toxic and dangerous chemicals remaining in gear after decontamination.1 As with all personal protective equipment (PPE), this concern applies to footwear. The contamination concern becomes particularly important when a department is deciding whether to purchase leather or rubber footwear for its members. Although the fire industry knows that leather footwear fits better and provides more stability underfoot, a major challenge is the long-held assumption that after working exposures, leather boots retain more chemicals than rubber boots.
To evaluate this premise technically, W. L. Gore & Associates, Inc., conducted a series of laboratory tests on leather and rubber boot materials to determine residual levels of chemical contamination after completing decontamination procedures. Surprisingly, the results ran counter to the industry’s assumption. Although both leather and rubber are contaminated during fireground operations, our testing showed that after a simple wash, rubber retained higher levels of tested chemicals than leather did.
To design its testing protocol, Gore followed the same methodology used in the Federal Emergency Management Agency (FEMA)-commissioned study Non-Destructive Testing and Field Evaluation of Chemical Protective Clothing.2 This protocol allowed Gore to evaluate both gross (on the surface) and matrix (within the rubber or leather) levels of residual contamination for chemicals referred to in various NFPA standards.3 Gore focused on a range of chemicals that firefighters will likely encounter in the field, including carbon disulfide (CS2), tetrachloroethylene, isooctane (gasoline), acrylonitrile, dimethyl formamide (DMF), and diethyl amine.
Based on the FEMA study procedure, a leather sample and a rubber sample from newly manufactured boot materials were each saturated for 30 minutes with one of the selected chemicals. They were then rinsed with cold water for 30 seconds and scrubbed with 1.2-percent liquid detergent using a soft brush for 30 seconds. The samples then underwent another 30-second cold-water rinse and were air-dried in a well-ventilated area for 16 hours at room temperature.
To ascertain the amount of chemical remaining on each sample, Gore evaluated it for evidence of gross and matrix contamination. First, each sample was visually inspected for any residue spots or stains, which would indicate surface contamination. Test specimens were then cut from each sample to evaluate the matrix contamination level of each chemical. Each specimen was placed in a separate airtight vial and subjected to a 30-minute thermal desorption at 160°C. The off-gas residuals were collected and quantified via gas chromatography.
When the testing was complete, Gore quantified and compared the results for the two footwear materials. After the saturating, rinsing, washing, rerinsing, and drying, no sample had surface contamination. However, for matrix contamination, every leather sample had a significantly lower amount of residual chemical than the rubber samples.
Perhaps the most interesting results for firefighters are those for isooctane (gasoline), because it is so frequently encountered at emergency scenes. The isooctane residuals remained relatively high for the rubber boot samples even after decontamination. In contrast, the leather samples were almost fully decontaminated of isooctane by the normal decontamination procedures.
Firefighters and PPE undergo extreme conditions and are exposed to many chemicals during firefighting; therefore, safety and protection are rightfully high priorities. Traditionally, rubber boots have been assumed to provide easier and more complete decontamination for reuse after exposure, even though leather boots are much more comfortable, breathable, and flexible. However, this study provides evidence that after normal wash and air-dry decontamination procedures, leather boot materials actually retain substantially lower amounts of contaminants at the matrix level than rubber boot materials.
1. NFPA 1851: Standard on Selection, Care, and Maintenance of Protective Ensembles for Structural Fire Fighting and Proximity Fire Fighting, 2008 Edition, Annex A.7.1.1A.220.127.116.11.
2. Carroll, T. R., and Schwope, A. D., “Nondestructive Testing and Field Evaluation of Chemical Protective Clothing,” Final Report, United States Fire Administration, Contract No. EMW-89-C-3045, Arthur D. Little, Inc., Cambridge MA, December 1990.
3. NFPA 1971: Standard on Protective Ensembles for Structural Fire Fighting and Proximity Fire Fighting, 2007 Edition, Section 18.104.22.168(4); NFPA 1991: Standard on Vapor-Protective Ensembles for Hazardous Materials Emergencies, 2005 Edition, Sections 7.5.1(5), 7.5.1(8), 7.5.1(9), 7.5.1(19); NFPA 1994: SStandard on Protective Ensembles for First Responders to CBRN Terrorism Incidents, 2007 Edition, Section 22.214.171.124(2)(b).
WILLIAM F. CANDY is the Americas product manager for technical footwear at W. L. Gore & Associates, Inc., and was a member of Gore’s new product development team for six years. Candy has a B.S. from Lehigh University and an M.E. from Villanova University, both in mechanical engineering.