Occupational hazards in the fire service take more than one form. Acute threats like heat stress can be immediately life-threatening on the fireground, while chronic exposures, particularly to carcinogens, represent a serious long-term risk that the International Association of Fire Fighters (IAFF) continues to emphasize through its cancer awareness efforts.
Fire departments can’t eliminate every hazard, but they can strengthen exposure control by addressing vulnerabilities in the protective ensemble where one gap has historically stood out: the hood and the skin around the face, jaw and neck.
The fire service’s first particulate-blocking hood was introduced in 2016 in response to RTI International’s Fluorescent Aerosol Screening Test (FAST) that highlighted particulate penetration at the hood interface. Today, fire gear continues to be a practical lever for reducing both heat stress and exposure to carcinogens.
Why the interface gets attention
A structural hood sits at an interface, overlapping the turnout coat collar, helmet and SCBA facepiece. It also sits in a high-heat, high-sweat area of the ensemble, so its construction can influence comfort and heat stress during work. At the same time, the hood-to-mask and hood-to-collar overlap is a high-deposition zone, where soot and smoke particulates can collect on the hood surface and in the overlap areas around the mask seal and collar line, thus creating a direct pathway for contaminants to reach the skin.
This is one reason particulate-blocking hoods gained adoption before they became a standard expectation. NFPA 1970 (2025) updated hood requirements by setting clear parameters:
- Structural firefighting hoods must be particulate blocking (now mandatory).
- They must demonstrate filtration performance through the hood composites, including the seams, not just the base fabric.
- The standard also couples particulate blocking with breathability expectations, including a cited Total Heat Loss (THL) requirement of 325.
- In addition, there are design/fit-related provisions (e.g., face opening and hem/coverage criteria) intended to improve protection at the interface, and guidance emphasizing that filtration capability is expected over nearly the entire hood surface.
What does particulate blocking mean?
In practical terms, particulate-blocking hoods add a barrier layer intended to reduce particle passage through the hood. In this way, they act like a filter with technology capable of blocking particulates at 0.2 micron in size or larger. A “micron” (µm) is simply a way to describe particle size at a scale too small to see — one micron is one-millionth of a meter. For perspective, a human hair is roughly 50–100 microns wide, while many smoke and soot particles are measured in single microns or fractions of a micron. When you see a spec like “0.2 micron and larger,” it’s talking about particles hundreds of times smaller than a hair, which is exactly the kind of fine contamination that can settle on the hood-to-mask and hood-to-collar areas.
Separately, FAST findings help visualize why hood performance at the face and neck matters. Using a fluorescent-tagged challenge aerosol at 2.5 microns, testing showed particles penetrated a standard FR knit hood and left concentrated deposits on the participant’s neck, cheeks, ears and jaw.
Together, these points clarify why many departments now assess barrier construction, interface coverage, seam integrity and even post-laundering performance in the evaluation of particulate-blocking hoods. With that context, the next question is practical: What should departments look at when comparing hood options for their own crews and operating conditions?
How to compare particulate-blocking hoods
Departments usually compare hoods using two performance metrics:
- Thermal Protective Performance (TPP)
- Total Heat Loss (THL)
Both numbers matter because a hood sits where firefighters feel heat quickly and where added layers can affect heat stress.
To compare hoods objectively, it helps to separate the decision into two parts: What the hood is built to do on paper and how it behaves in your specific ensemble.
Start with like-for-like criteria you can verify from published information: hood style and cut, the particulate-barrier approach, coverage area (including how far the bib extends) and the hood’s listed TPP and THL. Then move to fit and interface. Try each hood with the department’s issued SCBA and helmet, confirming that it maintains consistent overlap at the coat collar and a stable interface around the mask seal area through normal head and neck movement.
It’s also useful to recognize that particulate-blocking hood designs are not all built the same way, even when they are aiming at the same functional outcome. Some use a three-layer composite, where a dedicated particulate-blocking barrier layer (e.g., DuPont Nomex Nano Flex) is positioned between two flame-resistant knit layers (e.g., PBI/Lenzing) that provide thermal protection and durability; one published configuration is listed at TPP 28.3/THL 418. Other designs achieve particulate blocking in a two-layer composite, pairing an outer flame-resistant knit layer (e.g., Nomex/Lenzing [20/80%]) with a highly breathable, air-permeable inner barrier (e.g., Stedair PREVENT) that provides the particulate-blocking function; one published configuration is listed at TPP 24.8/THL 374.2.
In practice, two hoods can both meet particulate-blocking requirements yet feel and perform differently once they’re integrated into the full ensemble. The goal is typically to balance thermal protection at the head-and-neck interface (TPP) with sufficient heat loss and breathability (THL) to avoid adding unnecessary heat burden. Side-by-side comparisons help clarify the trade-offs, so departments can choose what best fits their operating conditions and integrates cleanly with their SCBA, helmet and coat.
Hood inspection and care
Even the best hoods on paper must deliver the same protection after they’ve been worn hard, washed repeatedly and cycled back into service. This is where inspection, cleaning protocols and replacement criteria become part of exposure control.
Inspection should follow the NFPA 1850 approach: Routinely check for damage and confirm that the hood still fits and interfaces correctly with the rest of the ensemble. Key actions include:
- Inspecting for rips, tears, cuts and thermal damage.
- Checking the face opening for stretched elastic or misshaping that could create gaps at the hood-to-mask interface.
- Inspecting for thinning material, pinholes or seam issues that may not be obvious. Perform a light test by holding the hood up to a bright light and looking for “light leaks” you might not see in normal lighting.
- Tracking the condition of the hood across laundering cycles and removing hoods from service when damage or fit issues appear.
Inspection matters because a hood can look acceptable on the outside while seams or barrier layers degrade. For deeper cleaning, repair evaluation or consistent processing at scale, many departments also use professional PPE care services to support their operations.
What departments can do next
A particulate-blocking hood program is not only a purchasing choice; it is selection, fit verification, inspection and laundering discipline. NFPA 1970 (2025) clarifies the expected baseline for particulate-blocking performance, and NFPA 1850 aligns hood care with a formal inspection and maintenance framework.
Departments looking to reduce face and neck exposures can start with three practical steps:
- Take inventory of the hood types currently in service;
- Verify they are certified to today’s requirements; and
- Standardize inspection routines so wear, damage or fit issues are identified before they become performance gaps.
By pairing certified particulate-blocking hoods with disciplined selection, fit verification, inspection and care, departments can materially reduce face and neck exposure without introducing unnecessary heat burden into the ensemble.
| WATCH: ‘This game of trade-offs’: Jeff Stull talks NFPA standards
ABOUT THE AUTHOR
Todd Herring is the vice president of product innovation and strategy for Fire-Dex.
