Is particulate matter important? Learn why, say IAQ experts

Particulate matter and carbon dioxide are important to track and remove to maintain indoor air quality (IAQ)

By Consulting-Specifying Engineer January 25, 2024
Particulates are compared to the size of a human hair. Courtesy: Consulting-Specifying Engineer

IAQ insights

  • Studies show that improving IAQ and IEQ can enhance worker productivity, but older buildings may face challenges meeting modern standards, particularly during a pandemic.
  • Various recommended limits for IAQ factors such as carbon dioxide, particulate matter (PM), formaldehyde, nitrogen dioxide and methane exist, with attention to maintaining optimal conditions and addressing potential health risks associated with air quality.

While watching the webcast HVAC: IAQ and IEQ is a much more complete overview, reviewing this transcript of the presentation helps define the topic better. It has been edited for length and clarity.

This information was presented by Emmy Riley, CEM, BEAP, WELL Performance Testing Agent, Energy Engineering Team Leader & Account Manager, Cyclone Energy Group, Chicago.

Why do indoor air quality (IAQ) or indoor environmental quality (IEQ) matter? Americans spend approximately 90% of their time indoors, according to the EPA and this indoor time is going to be usually either workplaces or homes or most buildings are some combination of a workplace and home. And studies have shown increase in worker productivity when improvements are made to IAQ and IEQ.

Older buildings may not necessarily be built up to the current codes and standards and older buildings tend to have notorious IAQ and IEQ issues, especially when we are looking at them from a pandemic viewpoint. I think that was one of the common things we ran into is the guidance didn’t necessarily match up with some of the older building designs and meeting some of those guidance from the professionals was hard for those older buildings to do.

But then also maintenance issues are common in both old and new buildings and can impact the IEQ even if they do meet the highest IEQ standards.

Here some of the IAQ recommended limits. The first one up is those comfort conditions. Sometimes the IAQ community can feel a little bit at odds with the energy conservation community and retro-commissioning work.

Dry air can get uncomfortable for people in the winter for folks in cold climates. My experience is that it’s just kind of a reality unless you have mechanical humidification and the more serious issues are happening when you’re in high-humidity conditions where things like mold and bacteria and dust mites can thrive and create unsafe conditions for occupants.

For carbon dioxide guidance, many regard 1,000 parts per million (ppm) particulate matter (PM) limit as the common upper indoor limit.

However, recently ASHRAE put out a position document on indoor carbon dioxide saying that it’s at best an indicator of outdoor air ventilation rate per person and that it’s not a very good overall metric of IAQ. And it’s more just a perception of human bio-effluence and the level of acceptance of their odors inside.

Particulate matter is basically a mix of solid and liquid droplets that are found in the air and it’s typically broken into two categories, nonrespirable and respirable. Figure 3 is showing PM 10 and PM 2.5. Compared to the diameter of a human hair, we can see that they’re very small.

Particulates are compared to the size of a human hair. Courtesy: Consulting-Specifying Engineer

Particulates are compared to the size of a human hair. Courtesy: Consulting-Specifying Engineer

PM 10 is anything less than 10 micrometers in diameter and those are typically inhalable particles like dust, pollen and mold. And if you’re in a season where we have a lot of allergens in the air like spring and fall, you’re probably going to see your PM 10 go up and the limits that you’re looking for from the EPA are 150. You’re trying to be below that.

For U.S. Green Building Council LEED and WELL testing in both of those, you’re looking to be below 50 micrograms per cubic meter. For PM 2.5, this is the parameter that we talked a whole lot about during the wildfires recently. And the reason why is because they are smaller, finer particles and they can embed deep in the lungs and make people develop health problems. And for people who are asthma sufferers, they can exacerbate asthma symptoms.

When you see the IAQ meter or the air quality index rather meter, the zero to 50 range is what you’re looking for. And then anything above a hundred, people in sensitive groups would start being recommended to go inside. And that’s because the PM or sometimes ozone gets kind of high.

And for the PM 2.5 limits, the EPA’s recommended high-end is 65 micrograms per cubic meter and for LEED PM 10; they both have the same recommended limit of 15 micrograms per cubic meter. And then the one that we were looking at a lot this summer with wildfire smoke was the recommendation from the World Health Organization of having a 24-hour max limit of 15 and an annual average max of five.

And then in terms of some of the other IAQ limits that we’re looking at, formaldehyde would count as a VOC. This can be kind of a tricky one to account for because VOCs, you’re looking at every VOC that exists everywhere. And the guidance on it varies. And what you’ll see usually talked about would be 220 parts per billion (ppb) guidance. But what you’re really looking for is the profile of how the VOCs are acting. If you have VOCs go up and then that VOC stops being emitted and your levels go back down, that’s really what you’re looking for. If they go up and stay up, you probably have an issue that you need to investigate.

Also talked about a lot recently is nitrogen dioxide (NO2) and methane, which is one of the products of combustion of fossil fuels. And when anytime in the news we’re talking about using unvented gas stoves, that’s a parameter that we would be looking at that can affect people’s health and can cause people to develop asthma. The limit on that one is 100 parts per billion as an hourly max.