This group brings together the best thinkers on energy and climate. Join us for smart, insightful posts and conversations about where the energy industry is and where it is going.


How To Fight Both Indoor Air Pollution and Climate Change at the Same Time

image credit: Awair, Inc.
Jay Stein's picture
Senior Fellow Emeritus E Source

Jay Stein, a Senior Fellow Emeritus affiliated with E Source, is one of America's leading energy technologists. Over the course of his over 40-year career he has played numerous roles, including...

  • Member since 2006
  • 79 items added with 52,887 views
  • Nov 10, 2021

Last fall, 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 a 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.

Bring eyesight to the blind

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 (see picture at the top) which sells for $149. 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

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 additional reduction in virus transmission, while achieving that same level of protection with outdoor air (colored lines) is far more expensive.

Source: Parham Azimi and Brent Stephens

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.


Matt Chester's picture
Matt Chester on Nov 11, 2021

Such an important but underdiscussed topic. When I was doing some reading into the WELL Building Standard, I was surprised by some of the statistics behind how directly air quality impacts productivity inside a building, expected sick time office workers would need, general happiness, and other factors. 

Jay Stein's picture
Jay Stein on Nov 21, 2021

Thanks, Matt. Yes, managing indoor air contaminants is vital to protect building occupant’s health and productivity. I also hope readers will take away from this article the importance of purifying that air in such a way that energy consumption is minimized. If climate change continues unabated, that is also going to negatively impact human health and productivity.

Jim Stack's picture
Jim Stack on Nov 12, 2021

Jay, Important information. It seems the HEPA filter like Tesla has as an option in their cars is the best.  I have read that half of the sales in China is because people want the filter to clean their air. QUOTE=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.


Jay Stein's picture
Jay Stein on Nov 21, 2021

You are correct that HEPA filters are the most effective at removing particles from airstreams. If you look at the chart above in my article, you’ll see that they’re also the most expensive to apply, with much of that cost attributed to the high amount of energy required to force air through them. That chart also shows that compared to MERV 13 filters, HEPA filters add little reduction in infection risk. That’s why, for buildings, MERV 13 and 14 filters seem to be the sweet spot at which infection risk is largely reduced, while simultaneously managing energy consumption. In cars, of course, the situation may be different. Manufacturers may take different approaches towards balancing particulate reduction and energy consumption.

Jay Stein's picture
Thank Jay for the Post!
Energy Central contributors share their experience and insights for the benefit of other Members (like you). Please show them your appreciation by leaving a comment, 'liking' this post, or following this Member.
More posts from this member

Get Published - Build a Following

The Energy Central Power Industry Network is based on one core idea - power industry professionals helping each other and advancing the industry by sharing and learning from each other.

If you have an experience or insight to share or have learned something from a conference or seminar, your peers and colleagues on Energy Central want to hear about it. It's also easy to share a link to an article you've liked or an industry resource that you think would be helpful.

                 Learn more about posting on Energy Central »