Since the advent of modern firefighter clothing following the initiative of Project FIRES by the International Association of Fire Fighter, there has been a requirement in NFPA 1971 for turnout clothing to provide continuous moisture protection. This was primarily included to keep liquids from entering the front closure and fly sections of the garments.
Other requirements have been included to ensure that the liner, including both the moisture barrier and thermal barrier, be extended to a specific distance to the outer shell hem at the collar, the sleeve ends, and bottom hem of the coat and to the waist and pant leg ends as part of trousers.
Liquid protection had been a rising concern for the fire service even before the IAFF Project FIRES. For some departments, the idea that firefighter clothing have waterproof characteristics dates back to the coated slickers and other clothing that functioned more like rainwear than what now has come to be appreciated as bunker gear.
It was not uncommon to find the use of coated outer shells 30 years ago. Whereas in past decades, liquid exposure primarily focused on hot and cold water, concerns have extended to fireground chemicals and contaminated blood and body fluids.
Providing protection
The manner in which the moisture barrier provides liquid protection is straightforward; this material is generally a laminate of a high temperature, flame-resistant polymer film to one or more textile fabrics.
As the film is continuous over the material layer. Seams between individual pieces of the moisture barrier found in the pattern for creating the liner convey this same physical barrier.
In contrast, the overall clothing item, whether coat or pants, only keeps liquids out if specific features are included to create overlaps and coverage of the body, particularly at closures and interfaces.
For example, the front closure of all turnout clothing includes a flap. In order for liquid not to enter the front of the coat, the flap must have moisture barrier as part of its layering. In addition, the it must butt up against the edges of closure area, and the inside of the shell along the sides of the front closure area must include strips of moisture barrier to accomplish overlaps of waterproof material
Similar arrangements must be made in the trousers fly. An entirely different type of design is used in the wrist area where not only must the liner extend to near the end of the sleeve, but a wristlet must be in place to help secure the sleeve on the wearer’s hand and keep all three layers in place.
The shower test
NFPA 1971 includes significant design features to accomplish the moisture and liquid protection. However, it also relies on a comprehensive test. The whole-garment liquid-penetration test, also known as the shower tests, evaluates complete coats and pants for their ability to prevent liquid penetration.
The test involves placing garments on a manikin that is already dressed in long sleeve, full leg undergarments intended to show water spots. The manikin is then placed on a rotating platform and sprayed by surfactant-treated water from five different nozzles for 20 minutes.
Three nozzles are positioned above the manikin and two are positioned to the lower sides. The test is intended to deliver a uniform spray to different portions of the clothing but in reality the majority of liquid impinging on the clothed manikin surface from the overhead nozzles and liquid runs off the manikin clothing by gravity.
A surfactant is added to the sprayed water for making the quality of water more penetrating and representative of liquids other than water such as hydrocarbons and blood, which can have surface tension values that are less than half of the value for water.
Since only the coat and pants are evaluated, the top portion of the collar is covered with a plastic bag over the manikin head and cups are placed inside the sleeve ends to prevent liquid spray from entering these areas. Thus, the evaluation of liquid-tight performance is limited to those areas of the manikin that are actually covered by the clothing.
Pass/fail performance is exclusively judged on the observation of liquid penetrating to the clothing interior. This may be in evidence by either wetness of interior layers or liquid spots on the underlying clothing worn underneath the coat and pants set.
Test shortcomings
While the test method is straightforward in principle, there is a substantial amount of criticism in the interest for its application to turnout clothing. The test is heavily dependent on how the manikin is dressed and obvious care is undertaken in how the closures are secured and the garments are oriented on the manikin.
Folds and creases in the clothing often create channels that direct liquid along various paths and sometimes into less protected areas, such as a collar area diverting liquid towards the front closure. An exposure time of 20 minutes is considered unrealistic if one considers the overall liquid exposure of test (five nozzles spraying approximately 0.8 gallon per minute).
Manufacturers that test their garments as part of the certification to NFPA 1971 often complain that the test is not reproducible and can create changes in garment features that result in overdesign that goes beyond end user expectations.
Despite the criticisms for the test, where complaints most have some validity, we are proponents of the shower test. That’s because firefighters are increasingly being exposed to fireground hazards that include a variety of liquids, much of it hose spray runoff, of varying degree of health effects as well as blood-borne pathogens.
Nevertheless, we agree that changes to the test may be needed to meet the intended level of liquid protection afforded to firefighters. After all, the hood is a porous knit with no barrier performance whatsoever.
A better mousetrap
Yet, liquid protection is one of those tradeoff areas. Firefighter want and need liquid protection, but overdesign for liquid-barrier performance creates an imbalance with other garment effects, most notably thermal stress/comfort, mobility, and ease of donning.
To this end, our company, International Personnel Protection, Inc. has undertaken a project sponsored by the Department of Defense’s Technical Support Working Group, to establish an improved liquid-integrity test for first responder protective ensembles. This project is aimed at revising or replacing the existing test with equipment and procedures that are more relevant to firefighter exposures, yet still provide a characterization of overall liquid protection.
In addition, our goal is to devise liquid penetration sensors using a simple electrical principle that provides a clear determination of penetrating liquid and will establish the ability to determine when and where the liquid penetration occurs.
This activity will involve a high degree of validation, particularly to show that the proposed method is reproducible with the concurrence of those laboratories performing the tests for product design and certification. We plan to provide a short survey that assesses end user expectations relative to liquid protection to guide this effort in addition to support from the NFPA’s Fire Protection Research Foundation for providing technical advice through an advisory panel.
