The Role of UV Lights in Summer Duct Sanitation

Summer in Spokane brings peak cooling loads, humidity around coils, and—more often than not—smoke intrusions from regional wildfires. To keep HVAC systems sanitary and efficient during this high-stress season, we deploy germicidal UV-C inside air handlers and ducts to suppress microbial growth on coils and in moving airstreams while pairing it with high-efficiency filtration for particles. As a local provider, Air Duct Cleaning Spokane (Spokane, WA) integrates UV-C with ASHRAE-aligned practices to raise indoor air quality (IAQ) without compromising safety.

UV-C in HVAC: What It Does—and What It Doesn’t

UV-C (200–280 nm, typically 254 nm) damages microbial DNA/RNA and inactivates bacteria, molds, and viruses on surfaces and in air. In HVAC systems, we use two complementary approaches:

• In-duct (airstream) UVGI to reduce viable microbes in circulating air.

• Surface/coil irradiation to keep coils, drain pans, and insulation free of biofilm that otherwise re-seeds air and robs efficiency.

These practices are recognized in ASHRAE’s position on infectious aerosols, CDC/NIOSH germicidal ultraviolet guidance, and laboratory test methods in ANSI/ASHRAE Standards 185.1 (airborne inactivation) and 185.2 (on-surface intensity). UV-C does not remove wildfire smoke PM₂.₅ or gases; that job belongs to MERV-rated and HEPA filtration and, optionally, carbon media. EPA’s residential air-cleaner guidance covers these distinctions.

Why Summer Is the Prime Time for Coil UV-C

Cooling seasons load coils with moisture; biofilms flourish, elevating coil pressure drop and suppressing heat transfer. ASHRAE documentation notes that UV-C keeps coils and pans clean and addresses biofilm-related fouling. In a commissioned field study (ASHRAE RP-1738), continuous coil irradiation produced a ~21% decrease in coil air-side pressure drop and a ~14–15% increase in overall heat-transfer coefficient (UA)—improvements that translate into measurable fan and compressor savings.

Spokane’s Smoke Season: Pair UV-C With Filtration, Not Instead of It

Wildfire smoke has become a seasonal reality here—Washington health authorities even warn that smoke-free summers are no longer guaranteed. For smoke days, we prioritize MERV-13 or better filters in central systems and portable HEPA units to cut indoor PM₂.₅; we keep spare filters on hand because they load quickly during smoke events. UV-C remains valuable for microbial control on coils and in air, but it won’t capture particles or VOCs from smoke; filtration and carbon are required. Public guidance from state and federal agencies reinforces these practices.

Design Specs We Use for Effective, Safe UV-C

Wavelength & sources. Germicidal systems typically use low-pressure mercury lamps peaking at ~254 nm; design and commissioning must prevent occupant over-exposure as outlined by occupational-health guidance.

Placement strategy.

• Coil irradiation: lamps downstream of the cooling coil continuously bathe wet fins and pans.

• Airstream disinfection: lamps upstream/downstream of the coil with tighter spacing to raise dose in moving air. These placements follow the engineering guidance published in ASHRAE’s UV chapters.

Intensity and dose considerations. Typical design guidance indicates coil-maintenance irradiance on the order of ~50–100 µW/cm² at the coil surface, while in-duct air-disinfection systems can reach up to ~10,000 µW/cm² depending on geometry and speed; exact values are engineered from lamp output, distance, airspeed, and target organisms.

Verification & standards. We request manufacturer data tied to ASHRAE 185.1 (airborne) or 185.2 (surface) testing. Where infectious-aerosol risk is a driver, we align with the risk-management framework in ASHRAE Standard 241.

Materials & maintenance. Continuous UV-C can degrade certain plastics and filter binders; we select UV-resistant media, inspect gaskets, and schedule relamping/cleaning so lamps sustain output.

Ozone & indoor chemistry. We use ozone-free devices and verify UL 2998 “Zero Ozone Emissions” where applicable. UV devices can influence indoor chemistry; proper application and ventilation mitigate by-products.

Performance & ROI: What Building Owners Can Expect

By restoring coils to “clean-coil” conditions and keeping them that way, UV-C reduces fan energy (lower pressure drop) and boosts cooling capacity (higher UA). The RP-1738 research documented ~21% lower coil pressure drop and ~14–15% higher heat-transfer coefficient after continuous UV-C—benefits that support energy savings when paired with proper filtration and commissioning. Field case work similarly shows year-over-year HVAC energy improvements when UV-C is maintained alongside filtration and system tuning.

A Spokane-Ready Checklist for Summer Duct Sanitation

1. Upgrade filtration to MERV-13 (or the highest compatible) and stock extras for smoke days; add portable HEPA in priority rooms.

   
   

2. Select UV-C type: airstream UVGI for airborne microbial risk; coil UV-C for cleanliness and efficiency—or a combined array.

   
   

3. Insist on standards: ask for 185.1/185.2 test data and UL 2998 verification for zero ozone.

   
   

4. Commission safely: shield lamps, verify irradiance, confirm no light leaks to occupied areas, and label service panels.

   
   

5. Operate smartly: run UV-C continuously across the cooling season; coordinate with ventilation and filtration targets during smoke episodes.

   
   

How We Integrate UV-C Into Summer Duct Service

We start with filtration and airflow verification, clean and inspect coils, then install UV-C arrays sized to the coil face area and duct geometry. We validate lamp output, check for material compatibility, and set maintenance intervals so output doesn’t drift below target. For smoke season, we stage filter changes and add room-level HEPA where occupants spend the most time. If you’re planning a mid-season tune-up or retrofit, scheduling with Air Duct Cleaning Spokane ensures UV-C is deployed as part of a complete IAQ stack rather than a stand-alone gadget.

CONCLUSION

UV-C is a proven, standards-backed tool for summer duct sanitation: it keeps coils sanitary, suppresses microbial growth, and helps recover HVAC efficiency—while filtration handles smoke and dust. A Spokane-ready plan blends UV-C + MERV-13/HEPA + ventilation best practices, validated against ASHRAE and public-health guidance, to keep indoor air cleaner and systems running at peak performance through the hottest, smokiest weeks of the year.

Learn why Spokane daycares should prioritize air duct cleaning in summer to reduce allergens, improve airflow, and keep kids safer—read the full guide here.

FAQs

1) Will UV-C eliminate wildfire smoke odors or haze? 

No. UV-C inactivates microbes; it does not capture particles or gases. Use MERV-13/HEPA for particles and activated carbon for odors, supported by fresh-air and recirculation strategies appropriate to smoke conditions.

2) Is duct-mounted UV-C safe for people and equipment? 

When properly enclosed and commissioned, UV-C does not leak into occupied spaces. Choose UV-resistant materials, verify zero-ozone labeling, and follow safety guidelines for installation and service.

3) What measurable performance gains are realistic? 

Independent field research has documented ~21% lower coil pressure drop and ~14–15% higher heat-transfer coefficient after continuous coil irradiation, supporting tangible energy savings when combined with high-efficiency filtration and routine commissioning.