Understanding UV exposure in firefighter PPE care

We have known for decades now that heat, abrasion, chemicals and repeated laundering take a toll on protective equipment. What receives far less attention is the role of ultraviolet (UV) radiation, a natural and well-understood source of material degradation in textiles, polymers and elastomers. UV exposure, especially from sunlight, can weaken fibers, break down moisture barriers, affect trim adhesives, and reduce the service life of critical ensemble components.

And while sunlight can cause measurable damage, departments frequently ask whether indoor fluorescent lighting presents a similar risk. Some firefighters recall older warnings that fluorescent lights could “fade bunker gear,” while others report storing gear in stations under fluorescent bulbs for years with no obvious consequences.

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What does the science say?

A review of polymer research, lighting engineering literature, laboratory testing standards, museum conservation work and UV-exposure studies shows a consistent conclusion: UV emissions from intact indoor fluorescent lamps are extremely low — typically 100 to 1,000 times less intense than sunlight [1] — and therefore are not considered a primary concern for degradation of firefighter protective clothing. The UV levels present in normal indoor environments simply are not strong enough to initiate the photochemical reactions necessary to weaken aramid fibers, degrade moisture barriers or damage elastomers (rubber materials).

However, as with any environmental factor, caution is warranted for very long-term indoor storage, particularly if PPE remains for years in direct view of large windows or overhead skylights, or in storage arrangements where fluorescent lighting is extremely close for long periods. The risk remains low but not zero. The key takeaway is that sunlight — not indoor lighting — is the real UV hazard that departments must control.

In this column, we summarize the comparative impact of sunlight versus indoor lighting, the science behind UV susceptibility in firefighter PPE, the test methods used to simulate UV aging, plus practical precautions that can extend the life of turnout gear while supporting the intent of NFPA 1850.

Understanding the UV difference: Sunlight vs. indoor fluorescent lighting

Sunlight reaching the Earth’s surface contains substantial UV-A (315–400 nm) and smaller — yet far more biologically and chemically potent — amounts of UV-B (280–315 nm). Clear midday sunlight typically delivers 30–50 W/m² of UV-A and 0.5–3 W/m² of UV-B, depending on geography. These irradiance levels are strong enough to destabilize and break molecular bonds in polymers and accelerate the degradation of moisture barrier films and elastomeric components.

By contrast, indoor fluorescent lamps emit extremely small amounts of UV. Modern fluorescent bulbs are engineered with phosphor coatings and glass envelopes that absorb nearly all the UV-B and UV-C (253.7 nm) generated by the mercury discharge. Only tiny amounts of UV-A leak through the glass, typically equivalent to 0.01–0.1 W/m² at typical room distances — more than two orders of magnitude lower than sunlight. Several technical sources support this finding:

• The Illuminating Engineering Society (IES) reports that intact fluorescent lamps release minimal UV, almost all of which falls within low-intensity UV-A ranges. [2]
• NIST spectral analyses of fluorescent lamps show UV output barely above background levels. [3-4]
• NIOSH technical guidance notes that daily UV exposure from indoor fluorescent lighting is roughly equivalent to less than one minute of sunlight. [5]
• Museum conservation studies (e.g., CIE Technical Report 157) confirm that fluorescent lamp UV intensities are safe for displaying vulnerable textiles for extended periods, provided UV filters or sleeves are in place. [6]

Taken together, this research demonstrates that indoor fluorescent light emits extremely low levels of UV radiation, suggesting low likelihood for degradation of textiles and other materials. Even prolonged exposure under fluorescent lighting generally produces no measurable polymer damage unless exposure periods span many years and lamps are positioned extremely close to the materials.

Sunlight, on the other hand, is a well-documented degradation agent. Field observations consistently show that turnout gear dried outside in direct sun fades more quickly, becomes stiffer and experiences premature weakening, especially along shoulder or knee creases where stresses are concentrated. Apparatus bays with large windows or translucent overhead doors also produce moderate UV exposure over time, especially during seasons with high sun angles. Therefore, while wholly indoor fluorescent UV levels are not a concern, sunlight must be actively managed.

Why PPE is susceptible to UV damage

Firefighting PPE incorporates multiple engineered materials, each with different UV susceptibility:

Aramid outer shell fabrics: Fibers such as para-aramid (Kevlar) and meta-aramid (Nomex) offer exceptional thermal stability but are sensitive to UV radiation. Research in Polymer Degradation and Stability and similar journals shows that UV exposure breaks these polymers, resulting in:

• Loss of tensile strength
• Fuzzing and surface brittleness
• Accelerated color fading (a visual cue of broader molecular change)

Significant degradation requires UV intensities far greater than fluorescent lamps emit (at least 400 times greater) [7], but direct sunlight easily exceeds these thresholds.

Moisture barriers (ePTFE and PU films): Moisture barriers are among the most UV-susceptible PPE components. Studies summarized in ISO/TR 20478 and barrier durability papers show:

• UV-B causes degradation of polyurethane films.
• ePTFE laminates can lose hydrostatic resistance when exposed to sunlight for extended periods.

Again, UV outputs from fluorescent lights are far too low to initiate these reactions, but sunlight is not [8].

Elastomers and plastics: SCBA facepiece seals, rubber trims, helmet components, and adhesive layers are all susceptible to UV-induced:

• Cracking
• Hardening
• Loss of flexibility
• Loss of adhesion

These materials are especially vulnerable in apparatus bays exposed to sunlight through doors or windows.

Reflective trim: Retroreflective materials rely on microprisms and adhesives, both of which can degrade under UV exposure. Sunlight accelerates delamination and dulling of reflective performance.

Across all these materials, the threshold for UV damage is significantly higher than what indoor fluorescent lighting provides, which is why fluorescent lamps do not appear in PPE durability concerns, certification tests or NFPA 1970 performance criteria.

What accelerated weathering tells us

Firefighter PPE materials undergo specialized testing to evaluate UV resistance. Importantly, none of these tests rely on indoor fluorescent lamps, because their UV intensities are far too low to produce measurable degradation within practical timeframes. Instead, widely accepted test standards use high-intensity artificial UV sources that replicate the damaging components of sunlight.

ASTM G154 (fluorescent UVA/UVB weathering): ASTM G154 uses UVA-340 or UVB-313 lamps, which emit controlled and intensified UV radiation that mimics the solar spectrum responsible for polymer degradation [9]. These lamps operate at irradiances that are 400-5,000 times greater far greater than indoor lighting to accelerate aging within hours or days.

ASTM G155 (xenon arc weathering): This method employs a xenon arc lamp that produces a full-spectrum simulation of sunlight, including UV, visible and infrared [10]. Xenon arc exposures are widely used to evaluate fabric fading, strength loss and polymer durability. A form of this test is used in NFPA 1970 for evaluating the continued water penetration resistance of moisture barriers when the barrier layer is exposed between an outer shell and thermal barrier. The test is also used for determining how the tear resistance of outer shells is affected by direct intense UV light exposure.

Two notes of interest here:

• Testing of moisture barriers is pass/fail based on the ability of moisture barriers encapsulated in the composite to show no leakage after an extended high-intensity UV exposure.
• The tear resistance of outer shell materials directly exposed to the same UV exposure must be reported and can be compared to its normal values when evaluated new and after a multi-conditioning process involving repeated laundering, heat exposure and flexing.

ISO 4892 series: This international standard also relies on xenon arc and UV fluorescent aging systems, not indoor lighting [11].

The fact that no material aging standard uses indoor fluorescent lamps tells us something important: Fluorescent lighting does not provide sufficient UV energy to drive polymer degradation at a measurable rate. Researchers and manufacturers universally turn to intensified UV sources because real-world indoor lighting does not induce significant material change.

Comparing real-world conditions: When UV exposure matters most

Fire departments should understand the conditions under which UV exposure becomes relevant:

• Outdoor gear drying: Allowing gear to dry on aprons, rails, fences or training grounds directly exposes it to high-intensity UV. Even a few hours of strong sun can contribute to cumulative damage, especially when gear is wet, which increases photodegradation rates.
• Apparatus bay exposure: Fire stations with glass bay doors, large windows or skylights can allow sunlight to strike PPE stored on open racks. Though less intense than being outdoors, this exposure is still significant relative to fluorescent lighting.
• Long-term display storage: Legacy gear displayed near windows can fade and degrade, though this primarily affects museum or ceremonial settings.
• Long-term indoor storage under close fluorescent lamps: While normal fluorescent lighting is not a hazard, storing PPE directly beneath unshielded fluorescent fixtures at extremely close distances (less than 12 inches) for years may create very slow cumulative fading. This is not typically operationally significant, but it warrants easy precautionary measures.

Practical precautions: What fire departments should do

Although fluorescent lighting is not a primary concern, departments should still adopt the following six practical UV-control measures that align with NFPA 1850 and extend gear life:

1. Avoid drying gear in direct sunlight

• Use shaded areas or indoor drying rooms.
• If drying outside is unavoidable, immediately remove gear once dry.

2. Protect gear in apparatus bays

• Install UV-blocking window film on apparatus bay doors or windows.
• Avoid leaving gear on open racks exposed to sunlight.
• Rotate gear positions if some spots receive more window light.

3. Use enclosed or opaque storage

• Closed lockers, cabinets or opaque covers prevent incidental sunlight exposure.
• This is particularly important for reserve gear stored for long periods.

4. Keep fluorescent lamps at normal distances

• While not a risk factor, avoid placing PPE just inches away from fluorescent lighting for multi-year storage.

5. Inspect for UV damage during advanced cleaning/inspection

• Signs include: Excessive or uneven fading; fuzzing or fiber stiffness; trim delamination; and/or cracked elastomers.

6. Maintain documentation

• Record when PPE is stored long-term, moved to new storage areas, or exposed to sunlight during drying.

Final notes

A consistent conclusion emerges across lighting engineering, polymer degradation science, museum conservation research and occupational health studies: Indoor fluorescent lighting does not provide enough UV energy to significantly degrade firefighter protective clothing. Sunlight, not indoor lighting, is the true aging concern. However, because PPE is often stored for long periods — sometimes years — departments should still manage very long-term exposure and avoid unnecessary UV exposure from windows or skylights.

This is good news for the fire service: Normal station lighting does not endanger your gear. At the same time, it reinforces the need for sensible UV-control practices that many departments may already be following without realizing it.

Bottom line: Turnout gear is one of the most essential tools firefighters rely on. Understanding how UV exposure affects it — and how to protect it — helps departments maintain safety, preserve budgets and extend the service life of their most critical equipment. With a few informed precautions and awareness of the scientific evidence, the fire service can confidently manage UV exposure in a way that supports both operational readiness and long-term PPE health.

Note: The views of the author do not necessarily reflect those of the sponsor.

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REFERENCES

1. Diffey, B. L. “Sources and Measurement of Ultraviolet Radiation.” Methods 28, no. 1 (2002): 4–13.
2. Illuminating Engineering Society. The IES Lighting Handbook. 10th ed. New York: Illuminating Engineering Society, 2011.
3. Nazaré, S., Davis, R. D., Peng, J. S., & Chin, J. (2012). Accelerated weathering of firefighter protective clothing: delineating the impact of thermal, moisture, and ultraviolet light exposures. US Department of Commerce, National Institute of Standards and Technology.
4. Davis, R., Chin, J., Lin, C. C., & Petit, S. (2010). Effect of Accelerated Ultraviolet (UV) Weathering on Firefighter Protective Clothing Outer Shell Fabrics. National Institute of Standards and Technology.
5. National Institute for Occupational Safety and Health (NIOSH). Health Effects of Occupational Exposure to Ultraviolet Radiation. DHHS (NIOSH) Publication No. 2010-103. Cincinnati, OH: NIOSH, 2010.
6. International Commission on Illumination (CIE). CIE 157:2004 – Control of Damage to Museum Objects by Optical Radiation. Vienna: CIE Central Bureau, 2004.
7. Wakatsuki, K., Matsubara, M., Watanabe, N., Bao, L., & Morikawa, H. “Effects of m-Aramid/p-Aramid blend ratio on tensile strength due to UV degradation for firefighter clothing fabrics and development of predictive equation for tensile strength. Polymers, 14(16), 3241.
8. Munevar‐Ortiz, L., Nychka, J. A., & Dolez, P. I. (2024). Moisture barriers used in firefighters’ protective clothing: Effect of accelerated ultraviolet radiation aging on their mechanical and barrier performance. Journal of Applied Polymer Science, 141(40), e56048.
9. ASTM International. ASTM G154 – Standard Practice for Operating Fluorescent Ultraviolet (UV) Lamp Apparatus for Exposure of Nonmetallic Materials. West Conshohocken, PA: ASTM International.
10. ASTM International. ASTM G155 – Standard Practice for Operating Xenon Arc Light Apparatus for Exposure of Materials. West Conshohocken, PA: ASTM International.
11. International Organization for Standardization (ISO). ISO 4892-2:2013 – Plastics—Methods of Exposure to Laboratory Light Sources—Xenon-Arc Lamps. Geneva: ISO.