indoor air quality

Forest fires pose indoor air quality challenge

Particulate matter triggers public health advisories in B.C. and Alberta
Thursday, August 17, 2017
By Barbara Carss

Outdoor air has been far from fresh in some areas of British Columbia and Alberta this summer. Smoke from a series of tenacious forest fires has prompted public health authorities in both provinces to issue recommendations for avoiding undue exposure.

B.C.’s aptly named Smoky Skies Bulletin, which provides a regularly updated list of regions of concern, also directs affected residents to potential relief. “Consider visiting a location like a shopping mall with cooler filtered air,” it suggests.

Indoor air quality specialists concur that larger commercial buildings are among the better places to be when outdoor conditions are compromised since HVAC systems typically incorporate air filtration. Depending on the filter’s efficiency level — known as MERV, an acronym for Minimum Efficiency Reporting Value — that could capture airborne particulate smaller than a micron. Nevertheless, prolonged poor air quality creates challenges for any kind of ventilation system.

“We rely on fresh air to flush out carbon dioxide. In the ideal situation, we’re bringing in lots of fresh air and we’re dissipating it around and flushing it outside,” says Curt LaMontagne, principal indoor environmentalist with C5 Plus Limited in Calgary. “In a situation like we’ve got now, you really don’t have good choices.”

Earlier this week, the air quality index climbed toward higher health risk readings in the Calgary and Edmonton regions. “The smoke smells like a campfire. Sunday night it was noticeable. By Monday morning, you could feel it on the back of your throat,” reports Julien Poirier, a project manager with the engineering consulting firm, WSP Group, also based in Calgary.

Although conditions later improved, Alberta Health Services recommends residential and automobile windows and vents should be kept closed when smoke can be smelled or tasted in the air. Closer to the source of the flames, air quality readings in the B.C. interior have more consistently hit high health risk levels throughout the summer, whereas the lower mainland has experienced occasional peaks interspersed with moderate and low-risk results.

Unlike gases, which can be mitigated via biofilters like aesthetically pleasing living walls, the contamination from forest fires is primarily fine particulate matter that humans and animals can inhale deeply into their lungs. Filtration or outright avoidance are the basic and really only operational strategies for controlling its presence indoors.

Filtration

Buildings certified under the WELL Standard or that have attained LEED credits for enhanced indoor air quality may be better placed to do this since both compliance paths specify MERV 13 or higher filters on intake units for outdoor air supply. That effectively traps particles as small as the nuclei of a sneeze droplet and up to 90 per cent of larger particles.

The MERV rating chart categorizes this as an attribute of “superior commercial buildings”, but it’s a plausible retrofit for a broader range of office stock. “Typically, most air handling systems can accommodate up to a MERV 13 filter,” Poirier affirms.

MERV 15 filters can be found in some high-performance commercial buildings. However, filters with higher ratings are generally used in more specialized applications such as health care facilities or pharmaceuticals manufacturing, and can be beyond the engineered capacity of fan systems found in many office buildings. Even moving up a few gradients from the more standard MERV 8 or 11 filters will increase energy loads since fans must work harder to draw air, but building owners may see the added energy costs as a reasonable trade-off in parts of the country where forest fires are common and/or increasingly frequent.

“Going from a MERV 8 to a MERV 15 is not going to double the energy load on the fans. It probably amounts to a fraction of a percentage in increased loads across the whole building,” Poirier says.

“Buildings should plan for accommodating potential future increases in air pollutants,” concurs Barbara Ciesla, senior vice president, strategic consulting, with JLL.

For example, the WELL Standard’s requirement that HVAC systems have the ability to accommodate carbon or combination particle/carbon filters creates manoeuvring room if outdoor air quality decline in the future. More broadly, the standard embeds the discipline of ongoing quality control and preventative maintenance.

“We design HVAC systems to perform to a certain level, but they must be consistently tested to make sure the actual performance — in this case, air filtration — is meeting intended performance,” Ciesla adds.

Monitoring intake

Regardless of filters, higher levels of pollutants outdoors inevitably become an indoor air quality issue. “Even if you’re filtering out 80 per cent of the particles, 20 per cent are getting through,” LaMontagne observes.

Adjusting air intake is a more delicate part of the response strategy since it requires a balancing of two less than desirable outcomes. “If you close the dampers or shut down the fans, carbon dioxide will build up; volatile organic compounds will build up. People with sensitivities will start to feel the exposure to these contaminants,” he warns.

Poirier also reminds building operators that building automation systems aren’t programmed for atypical times and will continue to draw air based on temperature triggers.

“You may want to disable your air-side economizer,” he says. “Otherwise, if the temperature drops to around 15 to 17 C, the BAS could start bringing in 100 per cent outside air. You want to minimize the outside air.”

British Columbia has announced that this is the province’s worst season for forest fires since records were first kept, with nearly 895,000 hectares already destroyed. A provincial website lists 28 “wildfires of note” as of August 17, defined as “highly visible or which a pose a potential threat to public safety.” Meanwhile, Alberta’s woes may not be so conspicuous, but the province’s extensive coal-fired electricity supply contributes to something of a poor air quality double whammy.

Barbara Carss is editor-in-chief of Canadian Property Management.

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