Protecting indoor air: Maintenance essential during wildfire season

Smoke can drift from burning wildfires to homes and buildings in communities hundreds of kilometres away.

British Columbia is cooling off in the wake of its most devastating wildfire season to date.

Scorching more than 13,000 square kilometres of the province, the wildfires prompted a nearly month-long State of Emergency in the summer of 2018. Smoke rising from the infernos severely degraded air quality–both indoors and outdoors–spiking pollution levels and putting HVAC systems to the test.

With back-to-back record wildfire seasons in the rear-view, Canada’s most westerly province must focus on preparation.

“Wildfires generate episodes of the worst air pollution that most people living in North America are ever going to experience,” said Sarah Henderson, senior scientist at the British Columbia Centre for Disease Control (BCCDC) and associate professor at the University of British Columbia’s School of Population and Health.

“This problem’s not going to go away… There’s no guarantee that 2019 is not going to be an equally bad wildfire season. Other parts of Canada are going to start seeing more and more of these extreme seasons and preparation is our best line of defence. Thinking well in advance of the wildfire season about how to keep indoor environments clean when the inevitable smoke arrives is going to pay off in the long run,” she added.

Fine particulate matter, one of many pollutants in wildfire smoke, poses the most serious health threat. Concentrations can reach 10 micrograms per metre cubed (µg/m³) on an average day in B.C. During periods of wildfire smoke, however, those concentrations can jump to 300 µg/m³.

“That’s a very large air quality impact,” Henderson said. “You can’t have outdoor air pollution like that without it getting indoors.”

The degree to which wildfire smoke infiltrates an indoor environment will vary based on the building type and HVAC system. Depending on proximity and size, wildfire–and all it burns up–can dirty coils or the water in cooling towers and overwhelm filters.

For Trane Canada representatives in BC, 2018 was a “bad year” for dirty and restricted condenser coils, resulting in high-pressure faults on air-cooled products.

“The filtration of smoke coming into buildings is, both from a not-triggering-fire-alarms to human health perspective, really the biggest thing. Much bigger than worrying about the outside equipment because it doesn’t really care too much about the smoke,” said Timo Lucas, systems and equipment leader at Trane Canada West and area manager for Vancouver Island and Kelowna, BC.

To maintain equipment and IAQ, Lucas said it is important to distinguish between visible smoke and invisible smoke–adding that the ideal filtration system would remove both physical particles as well as gas-phase contaminants.

Smoke is mostly ash, he said, and could be compared to dust. If it gets in the water of a cooling tower, for example, a contractor may need to increase the cycles of concentration, meaning to flush the water more often. Filters will also need to be changed more frequently on equipment during smoky periods.

“From either an open-cooling tower or a closed, you should probably, if it’s fairly smoky, pay a little bit closer attention. Maybe make an extra service visit to the equipment to see what’s happening with the water and/or if there’s any debris collecting on the fans,” Lucas said.

When it comes to protecting human health (see sidebar below), Lucas adds that while passive filters and HEPA filters are effective, he recommends electronic air cleaners, which remove harmful gas-phase contaminants and odour.

“You can actually smell ash and things like that, but you also smell and almost taste the gas-phase contaminants more,” he said. “For that reason, suppose you’re in a building that has a MERV 13 filter. Outside, you look across the street and you can see a blue haze in the sky. Indoors, the blue haze is gone, but you can still sort of smell and almost taste the smoke. The reason is that the gas-phase contaminants are still coming into the building through that passive filter. The way that those odours can be controlled or removed is to remove the gas-phase contaminants.”

Conversely, Kevin Delahunt–advisor and former director of business development at B.G.E Service & Supply Ltd., headquartered in Edmonton–warns that while both mechanical filters and electronic air cleaners effectively remove particulate, the latter can decrease in efficiency as it loads with the particulate and are not effective on odours and gaseous contaminants.

“Removing gaseous components, which could number in the hundreds, from smoke requires a different mechanism than removing particulate… To remove gaseous components effectively you would need a gas phase filter product in combination with particulate filters, which in most cases is not feasible financially or structurally,” he added. “Our advice to customers is: stay indoors, maintain a positive air balance in your building and monitor your filter system for fit and operation.”

While the bitter Canadian winter has taken a stronghold, preparing for the 2019 wildfire season will ensure HVAC systems can stand up to extreme episodes of smoke, protecting indoor air quality and human health.

“The reality is that most of us spend most of our time indoors. Even if only half of the smoke outside comes in, and it’s a really smoky day, you’re still getting a much higher exposure indoors than you would on a clean air day. Ultimately, the ideal approach to dealing with wildfire smoke would be the keep the indoor environment as clean as possible and keep smoke outside as much as possible,” Henderson said. <>

Author’s note: UL has created the validation for zero ozone air cleaning devices. See page 40 in the digital edition for more information.

THE HEALTH EFFECTS OF WILDFIRE SMOKE
The human body reacts to air pollution in the same way it might react to a bacteria or virus, and in response mounts an immunological attack, despite not actually being able to kill the pollution, Henderson said.
“When you breathe fine particulate matter–these are particles less than 2.5 microns in diameter–that pollution can penetrate quite deep into your lungs. It tends to generate irritation of the lungs and eyes and nasal passages… But it also generates inflammation,” she said, adding that effects will vary between individuals.
Common acute symptoms include watery eyes, a running nose, a cough or sore throat and a headache. When long-awaited rainfall extinguishes wildfires and cleans smoke out of the atmosphere, pollution levels drop quickly over 48 hours.
“As soon as the smoke goes away, those symptoms will generally go away as well,” Henderson said. Inflammation, however, presents a more serious concern, particularly for individuals with preexisting chronic conditions.
“What we don’t really know at this point is what the chronic effects of these smoke episodes are,” Henderson said. “We have a population living under very smoky conditions for two weeks, three weeks, maybe a month, we don’t know whether that affects their health for the year to come, for the next two years, for the next three years, for the rest of their lives.”
With the threat of increasingly extreme wildfires seasons, Henderson said its possible the long-term health of BC’s population will be affected.
“If there’s smoke of that magnitude outside, there’s definitely smoke inside as well. When these episodes occur, nobody can stop breathing, so everybody is exposed to that smoke. Some people are going to be more sensitive to it than others but the entire population is breathing in that air pollution,” she said.