A large majority of the indoor air quality (IAQ) problems that we investigate are caused by airborne particles. Also known as particulate matter, this involves the smaller dust, dirt, and debris found in the indoor air.

Some of this dust comes from the outdoors, and much of it comes from construction materials like gypsum wallboard or other organic products that are wearing or breaking down. Furnishings, such as carpet and furniture, are also a significant source of the particles. But honestly, a lot of it comes from us. Humans shed thousands of skin cells every day. Our pets at home also do, and that particulate can be carried into a building on our clothing; it’s all complicated and difficult to control.

Still, more particulate can leak into a building that isn’t sealed well (especially as the day’s winds blow against the building enclosure). Because of this, the question of how we can control it forms much of the consulting that we offer.

It appears that using MERV-8 air filters is the most common level of filtration in the commercial buildings we see. But MERV-8 filters are not very efficient. Recently, some of our clients and some of the federal buildings we visit are upgrading their air filters to a MERV-13 filter media. That’s great, but it still won’t address the particle source.

Over the years, we have investigated particle-related complaints in a large variety of offices. We can confirm that a majority of them were due to poorly organized, heavily cluttered offices. And that makes it challenging for the custodians to clean. The dust builds up in offices, and the occupant complains. The solution, however, is pretty easy to figure out — get organized!

While we routinely investigate complaints caused by particles that range in size from 0.3 to 10.0 microns (1 micron is 1/25 — or 400th of an inch), new concerns are being voiced for particles smaller than 0.1 microns. (These are referred to as ultrafine particles).

Ultrafine particles can carry chemical vapors much easier than larger sizes. Ultrafine particles are more prevalent in a cubic meter of air (as we sample them), and finally, the ultrafine particles can go much deeper into the lungs — so deep that they can bypass much of the body’s self-defense systems against breathing contaminants that are served by the lungs.

There is equipment to sample for ultrafine particles, but it is expensive and difficult to use. Heavy, cumbersome, and challenging to learn, the instrument has a long wand that extends some 4–5 feet away from the user. The user then slowly moves the wand from side to side, taking readings of the indoor air. Much like a Geiger counter, when the gauge levels go up, that indicates a direction to the source of particles. The user then walks in that direction, sampling as they go. Ultimately, the instrument will show the source of the higher particle counts and indicate an area to be repaired. We have used this equipment to find leaky window seals, poor wax ring seals, and even cracks in a slab in the above-ceiling spaces.

Finding and chasing odors using this ultrafine particle counter is an easy process. What won’t be easy (in the future) is finding and resolving occupant concerns for air quality when the regular (standard) tools don’t work.

We were charged with finding the pathway that cooking odors were taking to enter the U.S. Attorney’s Offices in one South Texas office building. The attorneys were on the fifth floor, while a large and popular restaurant was located on the sixth floor. We knew where the fajita-like odors came from, but we didn’t know how they got into the attorneys’ offices. Using the particle counter helped us identify window seals that were leaking in several areas. Even more surprising, we discovered that the cooking odors came from a floor drain in the restaurant kitchen! That drain-line ran above the ceiling of the attorneys’ offices. The ultrafine particle counter showed us higher numbers when we ran the wand around the bottom of the floor penetration (in the ceiling return), and this showed us something we could never have found without the instrument!

Occupant complaints in today’s environment can be addressed when found. But when the source isn’t properly identified, the leaky building and high ventilation levels (outdoor air) can dilute the source that may resolve the complaint.

Buildings are now being built tighter with better air controls. As that continues, the level of complaints will go down, but that doesn’t mean finding a solution to IAQ complaints will be easier. That’s why the need to find the sources of ultrafine particles will increase.

I don’t have a crystal ball for indoor air quality, but I do see the scientific community discussing an researching the concerns. And it is very likely that this is one issue that’ll haunt building owners, facility managers, and IAQ investigators like me long into the 22nd century.