(Bloomberg) —
As global temperatures rise, so too does the risk of more extreme wildfires. With those fires comes smoke and poor air quality.
Last year, smoke from Canadian wildfires drifted across the US and Europe, darkening skies and choking lungs. While this year’s Canadian wildfire season is expected to be less severe, smoke from fires in the western part of the country has already triggered air-quality alerts in surrounding communities and in parts of the US Midwest. Earlier this month, satellite images also showed smoke billowing from the Mexican Yucatan, a byproduct of fires set for agricultural purposes and a more extreme fire season.
Over the past decade in the western US, wildfire smoke has erased air-quality gains from regulations like the Clean Air Act, according to research published in Nature. Absent significant climate action, these perils are here to stay.
So what can people do to protect themselves? Bloomberg Green spoke to Amara Holder, a research mechanical engineer with the US Environmental Protection Agency’s office of research and development. Holder focuses on reducing exposure to wildfire smoke; she shared intel on what makes that smoke so deadly and how people can reduce their exposure.
This conversation has been condensed and lightly edited for clarity.
What is it about wildfire smoke, especially indoors, that is harmful for us?
The biggest pollutants of concern within wildfire smoke are fine particulate matter. These particles are smaller than 2.5 microns in diameter — smaller than a human hair. They’ve been associated with all sorts of diseases during smoke events like increases in asthma attacks, increases in coughing and wheezing, and increased mortality.
Often during smoke events we’re told we should go indoors. But smoke can get inside, too. How does that happen?
Wildfire smoke comes in with any crack or open space within your building. So if you think about an old home, you might have some cracks and gaps around your windows, or every time you open a door or window, that’s an opportunity for smoke to come inside. Heating, ventilation and air-conditioning systems can also actively bring in smoke. Some systems, especially in commercial buildings, have ventilation systems, so they’re actively pulling in outdoor air.
What is the best way of reducing smoke indoors?
With an air cleaner, which is a device that removes fine particulate matter from the air. A “true HEPA filter” is going to be the one that reduces particulate matter. [Ionizing air cleaners are not recommended because they can produce ozone, a lung irritant.]
You want to look for two things: a clean air delivery rate, or CADR, and an air cleaner that is certified by the American Association of Home Manufacturers. The clean air delivery rate is meant to give you an idea of what size space it will clean, so if you have a 300-square-foot room, you would buy an air cleaner with a clean air delivery rate of 300. A cleaner with a CADR of 100 would still reduce the concentrations of particulate matter in that room; it would just take longer to get it down and it may not be able to keep up with very high smoke concentrations. [Outside of the US, you might want to look for HEPA filters that meet H13 standard, and the CADR will be in meters.]
A common problem that we see in places that experience a lot of smoke: Air cleaners get turned off because people can’t hear over them. So one approach is to get [an air cleaner with a higher CADR than the square footage of your room] and just run it on a lower level. The caveat there is the clean air delivery rate is not specified for these other settings. So you really don’t know what you’re gonna get when you turn it down to the lower level. That’s one reason to also get an indoor air sensor. [Some air cleaners have built in air quality sensors.]
There’s also a do-it-yourself version, which is a box fan with a furnace filter. We recommend using a high-efficiency MERV 13 filter. [MERV refers to “minimum effective rating value.”] The MERV 13 rating is specifically for particles that are smaller.
There’s many different designs out there online and they are all effective, but what we found is most effective is these multi-filter designs. You don’t even have to attach the filter with duct tape or anything; you can use the suction of the fan itself so it’s very easy to put together. But if you do have some skill and you have some time on your hands, you can go crazy with the designs.
During the NYC smoke event, a lot of people said their air filters had a hard time keeping up because of leaky windows. Does weather stripping help?
I have not seen scientific evidence to back it up. I would never say, “Don’t do weather stripping.” I’m just saying I don’t know how effective it is. Certainly part of our recommendations is to try and remove any potential pathway for smoke to get in. We also even say limit door use if you can, so I think it’s worthwhile trying.
HEPA filters remove PM2.5 pollution, but with windows and doors closed, indoor CO2 levels go up. How do we manage that balance?
When CO2 levels are high, you can start to get headaches, feel groggy and even nauseous. If you’re having a CO2 issue, if you’re having headaches pop up, it might be that it’s best to get some fresh air into your space and run those air cleaners as much as you can to try and mitigate the smoke, or [spend some time in] another building that has a different type of ventilation system. Many commercial spaces will have demand-controlled ventilation. It’s monitoring how much CO2 is in the air, and then they bring in the ventilation to flush it out when it gets to be too high. [Many of these systems will also filter the incoming air.]
The New York smoke event was this sustained smoke, but we often see this sort of diurnal up and down to smoke concentrations [i.e. smoke levels going up and down throughout the day]. We recommend as soon as it gets good go outside open things. Flush it out. Enjoy the clean air while you can.
So I wake up in the morning, I check my phone app, and I see that it’s a bad air-quality day. What should I do?
I’ll speak personally. The first thing that I do when I see that it’s a bad air-quality day is I look at my indoor air sensors. I don’t have the tightest house, so I do see elevated PM within my house on those days. Because I have central air conditioning, I might turn on a fan-only mode if I don’t need heating or cooling because I’ve installed high-efficiency filters in my system. So I know that when I’m cycling it, particulate matters are being reduced, and I can prove that to myself with my sensor. As my fans are going, I see those concentrations drop off.
When it’s a smoky day and you’ve got smoke everywhere within your house, I would use the cleaner in multiple locations — wherever I’m going to be. So I have one for myself. And I have one for my son and it sits in his room so that he’s not going to be impacted by that smoke. I have children with asthma so another thing I do is I give them the medicine that they need to make sure that they’re safe, because I know that they’re going to have an intense exposure. And then finally, if we have a soccer practice in the afternoon, I might make that decision later in the day: Do I keep them out of that practice? Because if it’s outdoors, there’s no avoiding the air.
To contact the author of this story:
Kendra Pierre-Louis in New York at kpierrelouis@bloomberg.net
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