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Lessons Learned From Smoke Season 2023 About Protecting Indoor Air Quality

By Jay Stein on September 8, 2023

Source: Anthony Quintano (https://www.flickr.com/photos/quintanomedia/52958921436/)

When the smoke from Canadian wildfires spread through much of North America during the summer of 2023, it gave rise to an important question: How do you keep indoor air fresh when the outdoor air is polluted?

The 2023 wildfire season was an eye opener for many people, albeit a bloodshot one. Usually, it’s only the Western US that has to deal with wildfire smoke, but this year, smoke from Canadian forest fires poured down into eastern states, some over a thousand miles away. Many people sought refuge in buildings, where unbeknownst to them, the operators of those buildings faced a dilemma.

While at the time, building air may have been cleaner than outdoor air, indoor air is rarely pristine. It often contains carbon dioxide (exhaled by occupants), pathogens like viruses (also exhaled), volatile organic compounds (outgassed from furniture and carpets), and particulates (microscopic particles from burning fuel in gas stoves and fireplaces). Plus, whatever pollutants are outdoors find their way indoors. In homes we often mitigate these contaminants by opening windows, but commercial buildings—like offices, schools, and stores—are equipped with ventilation systems that automatically bring in outdoor air to dilute contaminants. That works fine when the outdoor air is clean, but what are building operators to do when the outdoor air is filled with smoke?

I spent a good deal of time this summer ruminating on this question and found that it begs a much bigger one. Of course, it makes sense to avoid breathing wildfire smoke. It contains particulates (abbreviated as PM2.5 in air quality apps and web sites) that are so tiny they penetrate deep into our lungs. Particulate pollution has been linked to numerous disorders, including asthma and cardiovascular disease.

But wildfire smoke isn’t the only outdoor air pollutant we need be concerned about. In some ways, other air pollutants are more insidious. Most are gasses, and many are odorless and colorless. We don’t immediately feel the irritation they’re causing, so they don’t get the same level of attention as wildfire smoke. Gaseous air pollutants include ozone, volatile organic compounds, and nitrogen oxides, and they also have the potential to damage both our respiratory and cardiovascular systems. Ozone is especially dangerous. According to the American Lung Association, “exposure to unhealthy levels of ozone air pollution makes breathing difficult for more Americans all across the country than any other single pollutant.”

Overall, the concentrations of virtually all US outdoor air pollutants dropped over the last few decades, but that progress isn’t uniform across the country. There are still plenty of places that all too frequently experience poor air quality. According to the American Lung Association, nearly 120 million Americans “live in places with failing grades for unhealthy levels of ozone or particle pollution.” Building operators in these high pollution areas can’t count on having a consistent supply of clean outdoor air.

What are these building operators to do? For one thing, they can install high-efficiency filters to remove both particulates and pathogens, like viruses. For another, they can install special filters designed to remove gaseous contaminants, like carbon dioxide and ozone, directly from indoor air. Air cleaned by a combination of high-efficiency filters, and special gas-removing filters, is often cleaner than outdoor air.

Building operators using such filter combinations don’t have to rely on having clean outdoor air to dilute indoor contaminants and can dramatically reduce their outdoor air intake. They also avoid the energy consumption associated with heating outdoor air up and cooling it down to room temperature. Not only do those energy savings help pay for such advanced filters, but they also reduce the extent to which buildings contribute to climate change. Which brings us full circle, as it’s climate change that’s now exacerbating our outdoor and indoor air pollution problems.

Smoke gets in your eyes

The most dangerous component of wildfire smoke is particulates, but wildfires are not the only source of particulate pollution. Others include factories, power plants, and gasoline and diesel motors. Particulates have been linked to cardiovascular disease, including heart attacks, strokes, chronic obstructive pulmonary disease, and asthma. According to the American Lung Association, they are responsible for nearly 48,000 premature US deaths annually. Some of the worst metropolitan areas for particulate pollution in the US include Los Angeles and Long Beach, Fairbanks, Phoenix and Mesa, and Detroit, Warren, and Ann Arbor.

Particulate pollution also finds its way into buildings, by seeping in through cracks and open windows, and being drawn in via fresh air intakes, but outdoor air is not the sole source of indoor particulates. Internal sources include cooking (heated food puts out particulates, and if you’re cooking on a gas stove, there’s also the combustion gasses), fireplaces, burning candles, and dust.

Of all the forms of indoor air contamination, particulates are the easiest to remediate. They can be removed from indoor air using high-efficiency filters, but few buildings are outfitted with such filters.

Lost in the ozone

Ozone is a gas molecule containing 3 oxygen atoms. It forms in the lower atmosphere when volatile organic compounds and nitrogen oxides mix, and are exposed to heat and sunlight. Volatile organic compounds typically come from burning fossil fuels, such as gasoline, diesel, and natural gas, and when fuels and solvents evaporate. Major nitrogen oxides emitters include cars, trucks, furnaces, and boilers. Wildfires also increase ozone levels.

The presence of ozone in the upper atmosphere is a good thing, as it absorbs ultraviolet rays. But here in the lower atmosphere, where we all live, it reacts with the linings of our lungs and airways, causing inflammation and respiratory system damage. Ozone is linked to asthma and chronic obstructive pulmonary disease. Children and the elderly are most susceptible. Some of the worst metropolitan areas, according to the American Lung Association, include: Los Angeles and Long Beach, Phoenix and Mesa, Denver and Aurora, Houston and The Woodlands, and New York and Newark.

Just like particulates, outdoor ozone penetrates into buildings. It’s also emitted indoors by printers, photocopiers, and some air purifiers. Fortunately, ozone reacts with interior surfaces, like walls and furniture, and breaks down, so indoor ozone levels are often about one-quarter of outdoor levels. Even at those reduced levels, because we spend more time indoors than outdoors, many people inhale potentially detrimental amounts of indoor ozone.

Climate change is making things worse

For decades after the EPA issued regulations authorized by the Clean Air Act, both particulate and ozone concentrations declined. In recent years, progress on both of those pollutants seems to have stalled out, probably due to climate change.

In the case of particulates, climate change is driving up temperatures, which drys out vegetation, leading to more wildfires. The number of days in which particulate pollution hit unhealthy levels in numerous US counties started rising dramatically about a decade ago, with many scientists warning the worst is yet to come.

The story is similar for ozone. In the West, climate change is driving hotter, dryer, sunnier summers, with more frequent stagnant air conditions. These are exactly the conditions that exacerbate ozone formation. According to the American Lung Association, “climate change is undercutting the progress we would have made” on ozone. Both particulates and ozone will continue to increasingly threaten our health, both outdoors and indoors, for the foreseeable future.

Filtration first

The first thing building operators can do is to install high-efficiency filters to remove particulates. Filter manufacturers express the effectiveness of their products using the Minimum Efficiency Reporting Value scale, which ranges from 1 to 20. The higher the MERV rating, the more effective a filter is at removing a wide range of particles from an airstream.

According to the US EPA, “upgrading to a filter rated MERV 13 or higher can be especially important during smoky periods to effectively remove fine particle pollution from smoke in the indoor air.” Most HVAC system filters feature MERV ratings from 6-8, which can remove some smoke-related particles, but probably not enough to effectively protect respiratory health.

Ozone, and other gaseous contaminants, can’t be removed from indoor air using ordinary filters. In theory, they can be removed using air filters infused with activated carbon. However, those filters are expensive and they require frequent replacement. Accordingly, they’re rarely used.

How to manage indoor air quality without using outdoor air

Once high MERV filtration is in place, building operators in places with high levels of ozone pollution may want to take the next step, and clean their indoor air without bringing in much outdoor air. The technology that makes this strategy possible is known as sorbent filtration. Sorbents are materials that gas molecules naturally adhere to on contact, and can be incorporated into filters formulated to absorb carbon dioxide, formaldehyde, and ozone. When sorbent filters are saturated, such that they can no longer absorb any more gas molecules, they are regenerated by forcing hot air through them. The absorbed gas molecules are then released from the sorbent filters and expelled outdoors.

While sorbents have been used for decades in spacecraft and submarines, currently, there’s just one manufacturer of such filters for buildings: enVerid, a young company based near Boston. It not only makes the filters but also incorporates them into modules containing fans, particulate filters, regeneration heaters, controls, and dampers (see picture below). Buildings that install these modules could potentially eliminate nearly their entire outdoor air intake and the pollution that comes with it.

Source: enVerid

Another problem with bringing in outdoor air is that it takes a lot of energy to warm it up to room temperature in the winter, and cool it down in the summer. Reducing the amount of air brought in avoids much of that energy consumption.

The National Renewable Energy Laboratory, a US Department of Energy lab that specializes, in part, in building energy efficiency, monitored three enVerid module installations: a wellness center and two office buildings. The NREL researchers found that the sorbent filters enabled building operators to reduce outdoor air intake quantities, reduce energy consumption, and meet or exceed their indoor air quality goals. How much energy individual buildings saved depended on numerous factors, including how their HVAC systems were functioning, and the local climate. In a Miami wellness center they determined that the enVerid modules reduced cooling energy by 37% during a 3-month test period.

In new construction, sorbent filters might add little or no cost to a project. Since they reduce heating and cooling loads, the cost of the heating and cooling equipment they displace is often similar to the cost of the modules. In existing buildings, the economics are more complicated. It’s possible that the sorbent filters could pay for themselves in 10 years, based on energy savings alone. In buildings where the occupants are sensitive to ozone and other air contaminants, the health benefits could exceed the sorbent filter costs in much less time.

Here’s what you can do

If you’re interested in protecting the air in buildings, you’ve got different opportunities depending on who you are. If you’re designing a new building in an area with high levels of ozone and particulate pollution, your opportunity is clear. By specifying a combination of MERV 13, or higher, and sorbent air filters, you may be able to produce a building that better protects the health of its occupants and consumes less energy than a typical building, at little to no additional upfront cost. How can you tell if your buildings is in a high-pollution area? Check the American Lung Association’s annual State of the Air Report. It contains data for high ozone and particle pollution days for nearly every county in the US.

If you’re an operator of an existing building, or a commercial building occupant, you can figure out whether you need upgraded air cleaning systems by monitoring indoor air quality with handheld or portable monitors. For example, the Awair Element monitors carbon dioxide, volatile organic compounds, and particulates, and is available online for $209. For policy wonks, you can advocate for national and local governments to adopt indoor air quality standards for commercial buildings.

For the rest of us, who want to be able to seal up our homes on high ozone days and still breathe easily, you may be wondering when a sorbent filtration system will be available for residences. I posed this question to Christian Weeks, enVerid’s CEO, and he told me such a product is technically feasible, and his company is working on it. If the market for a premium residential indoor air quality product develops, he told me, it might be available in just a few years.

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Returning Workers Demanding Safe Indoor Air Are Driving a Revolution in Air Conditioning Systems

By Jay Stein on February 1, 2022

Building air conditioning systems aren’t protecting the air we breathe and workers returning to buildings are demanding change. Upgrading those systems without contributing to climate change will take innovative public policies and technologies.

During the fall of 2020, between the second and third waves of the Covid-19 pandemic, the owner of the gym I work out at asked my advice on how to keep her building’s air safe from COVID-19. She asked because my wife had shared with her an article I’d written on upgrading heating, ventilating, and air conditioning (HVAC) systems to reduce airborne virus transmission.

Her quandary involved a proposal from her air conditioning contractor to install an electronic air cleaner. It was more expensive than she could afford, but if it would protect her members’ health and enable her gym to return to full occupancy, she was willing to look for the money.

I found some experts concerned that this system might not be effective or could produce harmful byproducts, so I advised her not to buy it. Instead, I suggested she ask her contractor to upgrade her system’s filters.

Her contractor refused. She tried another contractor, but he also insisted on the same electronic air cleaner. I told her I’d find her a contractor, but none I contacted were interested in doing that work or set up to do it at a reasonable cost.

In the end, she decided to focus on bringing in sufficient outdoor air, which she monitored with a handheld carbon dioxide meter. That wasn’t the most energy efficient choice available, but at least didn’t waste money on a questionable technology.

A few weeks later I got an email newsletter from the proprietor of the restaurant a few blocks from my house, bragging about how he had installed the very same electronic air cleaner and how safe his dining room would now be.

I drew several conclusions from this experience. Building owners and operators were attempting to upgrade their HVAC systems to mitigate infectious diseases, but didn’t know how in a way that was both effective and didn’t run up their energy bills. Neither did the technicians they relied on. And nobody had the information to determine how well their systems were now performing this task, or how upgrades could improve performance.

As we anticipate the end of the pandemic and plan to return to buildings en masse, millions of building operators are facing the same HVAC upgrade demands. Doing these upgrades in the most energy efficient way could significantly improve health conditions with little to no increase in energy consumption. Upgrades made in a more typical way could increase HVAC energy consumption 2-5 times, adding to the energy demands that are driving climate change.

New public policies and technology can empower governments and trade associations to enable building operators and technicians to collect and interpret air quality data that informs healthy and energy-efficient solutions. Without a massive campaign on this front, however, building owners and operators may be left with solutions that waste energy, fail to protect building occupants, or both.

The pandemic as teachable moment

“Before COVID-19, to the best of our knowledge, almost no engineering-based measures to limit community respiratory infection transmission had been employed in public buildings (excluding health care facilities) or transport infrastructure anywhere in the world, despite the frequency of such infections and the large health burden and economic losses they cause.”

So wrote a group of nearly 40 of the world’s leading indoor air scientists in a recently published manifesto. This “Gang of 40,” as I call them, explained how respiratory infections are spread by tiny liquid droplets exhaled by infected people and circulated throughout building air. Not only have few building HVAC systems been designed to remove them or inactivate their contained viruses, many have been implicated in spreading them.

One culprit for this situation is a lack of indoor air regulations, standards, or guidelines. The U.S. Environmental Protection Agency doesn’t regulate indoor air the way it regulates outdoor air. The country’s most important standards for building ventilation come from the American Society of Heating, Refrigerating and Air-Conditioning Engineers (ASHRAE) — and with the exception of health care facilities, those standards don’t take infectious respiratory diseases into account.

Surveys of workers taken during the pandemic indicate that this lack of standards is a big problem. One survey conducted by building technologies giant Honeywell found that 47% of U.S. executive-level workers believe “outdated ventilation systems” were the “biggest threat” to workplace safety. Concerns like these are bound to drive widespread HVAC system improvements.

The air the air is everywhere

Coronaviruses are not the only threats lurking in indoor air. Others include microscopic particles — known as PM2.5 and PM10 because they are 2.5 or 10 micrometers across or smaller — carbon monoxide, volatile organic compounds like formaldehyde and solvents, ozone, biological materials like mold and dust mites, nitrogen oxides, radon, and pathogens including viruses and bacteria. They come from indoor sources including fumes from combusted natural gas and wood, cleaning supplies, paint, furniture, pets, and our exhaled breath, as well as outdoor pollutants such as wildfire smoke and car exhaust that seep in through open windows and cracks in our buildings — or are brought in with ventilation air.

Indoor pollutants can cause or exacerbate eye, nose, and throat irritation, headaches, fatigue, asthma and other respiratory diseases, heart disease, cancer, and cognitive impairment. Researchers have also found that high levels of PM2.5 are correlated with higher levels of COVID-19 infection. Any nationwide attempt to upgrade HVAC systems to minimize infectious disease transmission must also deal with these other contaminants as well.

It all starts with standards

When diseases were spread through food and water, governments passed standards for food and water processing, and put a cadre of officials in charge of enforcing them. The Gang of 40 called for a similar system for indoor air quality: “In the 21st century we need to establish the foundations to ensure that the air in our buildings is clean with a significantly reduced pathogen count, contributing to the building occupants’ health, just as we expect for the water coming out of our taps.”

Such an indoor air quality revolution would start with government standards setting limits for key indoor air contaminants, based on building types and uses. But meeting those standards will require monitors to see how buildings and individual spaces are meeting them.

The saying “you can’t manage what you can’t measure” applies here. For centuries, building owners and occupants have lacked information on indoor air quality. A new generation of relatively low-cost air monitors is starting to change that. They measure temperature, humidity, carbon dioxide, PM2.5, and total volatile organic compounds, although not all the available monitors measure all those parameters. Most hook up to some sort of phone app or dashboard and analyze how the levels measured compare to safe ranges — although without national standards, these safe ranges are often based on the manufacturers’ judgement.

One example is the Awair Element, a smart-speaker-like box which sells for $299. It measures all the parameters listed above and features a rudimentary built-in display, as well as a smartphone app for more detailed information, trending, and analysis.

Last year, a team of scientists from locations as diverse as the Institute for Renewable Energy in Italy and the U.S.-based Lawrence Berkeley National Laboratory tested 8 different monitors under a variety of conditions, and found that the Awair product was the most accurate of the group. Making such measurements in a low-cost device is difficult, and even the Awair product registered errors in the range of 50% to 80% for some parameters and conditions. Still, the scientists concluded that such monitors “could be suitable for measurement-based indoor air quality management.”

Monitors like these could make us all much better informed indoor air consumers. Occupants could know when to open windows or leave when air is unsafe. Building operators could make data-informed decisions about how to adjust HVAC systems, or use smart controls to ramp up airflows to densely occupied rooms while turning down airflows to others. Operators and controls could make comprehensive decisions that both protect our health and minimize energy consumption.

The human factor

This revolution in indoor air quality monitoring will also require building operators skilled in using that data to improve HVAC system operation. It’s vital that they do so in a way that minimizes energy consumption as climate change is also an increasingly dire threat to human health.

Indeed, numerous scientists have concluded that climate change is also worsening indoor air. Cleaning up indoor air at the expense of increased energy consumption just propels us further down that negative spiral.

Breaking that cycle is going to take more than access to data. In the words of William Bahnfleth, an architectural engineering professor at Pennsylvania State University, and a leading member of the Gang of 40, “simply dumping data on building occupants or operators won’t be very helpful if they don’t understand it.”

Clearing the air

To understand how building technicians could use data to manage HVAC systems, let’s review the basics. To generalize, there are two kinds of indoor air pollutants: gaseous (like carbon monoxide and formaldehyde) and particles (like soot and viruses). There are also two basic techniques for removing those pollutants: dilute them with outdoor air or blow air through filters.

Many building operators turn to outdoor air dilution because it’s relatively easy and works on virtually all indoor air contaminants. But it takes a lot of energy to warm up outdoor air in the winter and cool it down in the summer, and it can be downright counterproductive when outdoor air is more contaminated than indoor air — such as in the West during wildfire season.

Filtration is far less energy intensive but can also waste energy and damage fans and other equipment if the filters aren’t properly selected, sized and installed. Also, filtration only works on particles, not gaseous contaminants.

The most energy-efficient means to manage indoor air quality in most buildings is to bring in just enough clean outdoor air to dilute gaseous pollutants to safe levels, and then remove particles via filtration. Filters are rated according to a metric dubbed Minimum Efficiency Reporting Value, which ranges from 1 to 20 in terms of effectiveness at removing particles. Most commercial building HVAC system filters feature MERV ratings from 6 to 8, but the sweet spot at which human health is effectively protected while consuming a minimal amount of energy is at MERV 13. (see image)

**Source**: Parham Azimi and Brent Stephens

Caption: This chart from Illinois Tech shows that filtration is a far less expensive and energy intensive means to reduce virus transmission via heating and air conditioning systems than outdoor air dilution. Filters more effective than MERV 13 (on the black line) cost more to deploy, but provide little reduction in virus transmission, while achieving that same level of protection with outdoor air (colored lines) is far more expensive.

What not to do

Electronic air cleaners whose vendors claim they can remove pathogens from airstreams or deactivate them are the subject of much controversy. Some of these devices work by electrically charging particles, like viruses, while others shine ultraviolet light inside ducts. Some were tested by well-respected laboratories and found not to produce the same results claimed by their promoters or were found to release harmful byproducts. Many manufacturers released their own tests that were found lacking by leading indoor air scientists. For example, one manufacturer tested a product intended to clean an entire room by placing it in a small box.

“If you are considering an in-duct air cleaner for your heating and air conditioning system, if you have to plug it in, then it deserves extra scrutiny,” said Dr. Brent Stephens, who runs the Built Environment Research Group at Illinois Tech. With such a profusion of conflicting test results, applying that scrutiny is not easy. It’s probably best to avoid electronic air cleaners until standardized test results are available.

Calls for training are gaining

In my observation, it’s rare that building operators and technicians reconfigure their systems to use MERV 13 or higher filters. But to be fair, upgrading existing HVAC systems to mitigate airborne infectious diseases and other contaminants is challenging, even for experts. According to a team of scientists from Johnson Controls and MIT, “the best course of action can vary significantly from building to building and even within the same building depending on weather conditions or occupant behavior.”

Certainly, smarter HVAC controls and software that analyzes indoor air data would help, but it’s hard to imagine they’d be sufficient. Pennsylvania State University’s Bahnfleth is calling for education and training programs from government agencies and ASHRAE to help disseminate the skills needed to put these technologies to effective use.

Air America

The agenda proposed by the Gang of 40 and others — standards, monitoring, and training — is at its earliest stages. Perhaps, as with past pandemics, when this one ends it will soon be forgotten, leading to few changes in public policy or technology. For those committed to a different outcome, there’s much to be done. Policy wonks can advocate for government action to support all three elements of the agenda. For investors, opportunities lie in the budding air monitoring market and companies with indoor air management expertise.

As for the rest of us, there aren’t yet any easy answers. We can install air monitors, but what to do with the data is problematic. If our monitors tell us that our readings are out of range we can open our windows — if the outdoor air isn’t clogged with wildfire smoke. If particulates are too high, we can look for an HVAC contractor with the expertise to upgrade our filters to MERV 13. I wish I had a better answer for you, but this is a major problem and it’s going to take time to work out.

This article was originally published as How To Fight Both Indoor Air Pollution and Climate Change at the Same Time on Energy Central.