Tag Archive for: Odour reduction

UV-C germicidal irradiation has been the industry default for HVAC air and coil disinfection for over two decades. It works. Properly specified, a UV-C system reduces airborne bacteria, mould and viruses through the airstream and keeps cooling coils free of biofilm — which independently saves on cleaning costs and recovers the system efficiency that mould-fouled coils silently rob you of.

But for an increasing number of commercial environments, UV-C alone is solving half the problem. Odours and volatile organic compounds (VOCs) sail straight through a UV-C-only treatment with no measurable reduction. And those are exactly the contaminants occupants notice — and complain about.

This is the gap that photocatalytic oxidation (PCO) combined with activated carbon catalysts is now closing. It’s worth understanding when it matters, when it doesn’t, and how to specify it across project scales.

The Three Categories of Indoor Air Contamination

Anyone designing commercial HVAC already knows this implicitly, but it’s worth stating cleanly because it determines what technology you need:

For a standard commercial office with reasonable outside-air rates, addressing categories 1 and 2 is usually enough. The dilution from ventilation handles the chemical load.

For an increasing number of building types, that’s no longer true.

Where The VOC/Odour Problem Becomes a Specifier Problem

Some commercial environments have an atypical VOC and odour load — significant enough that the standard “good ventilation plus filters plus UV-C” approach leaves residual contamination that occupants notice. Common examples:

• Fire stations. Firefighters return with PAHs, fuel residues, combustion VOCs and smoke odours bound into gear and equipment. These off-gas inside boot rooms, truck bays and living quarters that frequently share an HVAC system. Australian research (Banks et al., 2020) has documented elevated PAH and flame-retardant levels in fire station air and dust, with peer-reviewed studies reporting associations between firefighter exposure and elevated cancer and respiratory disease risk.
• Aged care and healthcare. Cleaning chemical residues, body fluid odours, and high-volume disinfectant use create a continuous chemical load alongside the biological one. Occupants are often immunocompromised and odour-sensitive.
• Restaurants and food service. Cooking VOCs, grease aerosols, and the long-tail of food odours that lingers in soft furnishings and recirculates through the system.
• Gyms and fitness centres. Body odours, cleaning products, rubber off-gassing from new flooring and equipment. Member complaints about “the gym smell” are an HVAC specification problem, not a cleaning problem.
• Manufacturing and laboratories. Process VOCs, solvents, adhesives. Often the local exhaust is properly designed but the makeup air system recirculates residual contamination through occupied office spaces.
• Multi-tenant commercial. One tenant’s cooking, dry-cleaning or hair salon affects every neighbour’s IAQ through shared air handling.

In each of these, the building owner’s actual complaint isn’t biological. It’s “the place smells”, or “there’s chemical residue in the air”, or “staff are reporting headaches”. UV-C addresses none of those.

How Photocatalytic Oxidation (PCO) Closes the Gap

The Performance Numbers

Manufacturer testing on the APCO platform (Fresh-Aire UV, USA — the technology behind both residential APCO-X Ultra units and the commercial APCO Rack System we distribute in Australia) shows:

Two things worth noting from the published data. First, the biological figures are consistent with conventional UV-C performance — adding the PCO layer doesn’t compromise the disinfection function. Second, the gap between lab and field VOC numbers is honest. Real environments have higher airflow rates, lower contact times, and varied contaminant loads. A ~60% reduction in real-world VOC concentration is still a substantial change to occupant experience, particularly for odour-driven complaints.

The APCO platform has won the AHR Innovation Award in the IAQ category and carries UL 2998 zero-ozone validation, CARB certification, ETL and CE marks.

Worked Example: A 32″ APCO Rack On a Mid-Size AHU

Headline percentages only tell you so much. To make this practical, here’s an estimation of progressive odour and VOC reduction in a real-world installation scenario — a single 32″ APCO Rack System fitted to a cooling coil typical of mid-size commercial AHUs.

With ~9.23% of the airstream being treated per pass and 8 air changes per hour, the cumulative reduction of an existing odour or VOC load (assuming no new load being introduced) builds progressively. Untreated fraction after n passes is (0.9077)ⁿ.

For larger coils or higher VOC loads, a 46″ or 60″ APCO Rack — or a multi-rack configuration — improves single-pass coverage substantially and shortens these clearance times. Sizing is what we help consultants work through on a project basis.

Calculation is an estimate based on manufacturer cell geometry, stated single-pass photocatalytic efficiency, and standard recirculating-airflow modelling. Real-world performance varies with specific contaminant species, humidity, lamp age, and load intensity. We don’t publish guarantees on these figures; we provide them as a sizing reference for technical discussion with consultants.

Scaling the Specification: From Residential to Large Commercial

One of the practical advantages of the APCO platform is that the same core technology — UV-C plus PCO/carbon cells — scales across system sizes. Specifiers can apply consistent IAQ logic across a project portfolio without learning a different technology for each scale.

The Rack System is what we’d typically specify for fire stations, larger aged care facilities, hospital wings, hospitality kitchens, multi-tenant strata buildings and any commercial AHU above the residential size envelope. For mixed portfolios — for example a multi-site fire service with stations of varying age and AHU size — a single product family across the project simplifies installation, spares stocking and ongoing service.

When PCO + Carbon Is Worth Specifying (And When It Isn’t)

Adding PCO to a UV-C specification is a cost variation, not a free addition. Here’s the honest framing we offer consultants:

Our position with consultants is straightforward: don’t add PCO to a project that doesn’t need it. But don’t omit it from a project that does — and then have the building owner come back in 18 months asking why the place still smells.

Further Reading

For specifiers wanting to dig deeper into the firefighter exposure research that has driven recent interest in PCO for fire stations, the Australian peer-reviewed work is a good starting point:

• Banks et al. (2020) — PAHs and flame retardants in air and dust from Australian fire stations. Environment International. PubMed link
• Banks et al. (2021) — Australian firefighter PAH exposure in simulated compartment fires. International Journal of Hygiene and Environmental Health. ScienceDirect link
• CDC / NIOSH — PAH exposure assessment in fire houses. CDC archive

Australian Ultra Violet is the authorised Australian distributor for the Fresh-Aire UV APCO platform, including residential APCO-X Ultra and commercial APCO Rack System. We supply HVAC contractors, mechanical consultants and facility owners across Australia.