Keeping close tabs on the amount of moisture in the ductwork can prevent foul odors from wafting through the building. Instruments such as the Fluke 975 AirMeter can help. Image courtesy of Fluke Corp.


The problem isn’t just confined to high school locker rooms. Perhaps you’ve entered a building and smelled it yourself: An odor something like dirty socks greets you as you walk in.

People complain. Maybe even you complain. And then, hopefully, Warren Lowe, an HVAC maintenance mechanic for a major Midwest electric utility, arrives with his Fluke 975 AirMeter tester.

Lowe keeps the heating and cooling systems tested and tuned at six engineering and maintenance service centers around Muncie, Ind. These large buildings - up to 150,000 square feet - house all the people and equipment needed to design and maintain electrical transmission facilities: up to 100 line and station mechanics, storeroom technicians and office personnel.

A trained HVAC technician with 15 years experience, Lowe visits the buildings monthly to monitor each one’s heating and cooling system. Part of the job is calculating and adjusting the outside-air percentage added to the indoor air supply. Lowe calculates for health, comfort and code requirements.

“Keeping people healthy and comfortable go hand in hand. Happy workers are productive workers,” Lowe said. “If you don’t bring outside air in, you’re going to get a buildup of carbon dioxide (CO2) from the people.

Image courtesy of Fluke Corp.

Code requirements

“It’s a requirement by code that you bring in 10 percent outside air. You don’t have any choice,” he added.

Lowe says he focuses on outside air because it actually makes his job easier.

“Fresh air is usually clean air,” he said. “It makes people feel better and keeps the building from being stuffy or stale.”

People produce CO2 through normal breathing. While it is not toxic, its accumulation to excessive levels can indicate an inadequate amount of outdoor air is being added to the HVAC system. High levels may also indicate the risk that more toxic air contaminants, such as formaldehyde, are accumulating.

The Fluke 975 AirMeter calculates the percentage of outside air by comparing the percentage of carbon dioxide in return air against the CO2 concentration in outside air. It also calculates outside air by comparing the temperatures of return and outside air.

“What you want is about 300 to 600 parts per million of CO2,” Lowe said. “Above that, around 1,000 ppm, people start getting headaches, and above that, they start getting sick.”

Image courtesy of Fluke Corp.

In the balance

But incorporating the right percentage of outside air requires a delicate balancing act. Too little, and CO2 builds up. But add too much outside air, especially in the hot, humid Indiana summertime, and you may get a whiff of dirty socks.

What makes it difficult is that Lowe isn’t the only one adding outside air to the mix. His Muncie facility, for instance, includes 35 overhead doors to the outside, each measuring 20 feet tall and 20 feet wide.

“We have overhead doors throughout our building,” Lowe said. “You open an overhead door and open a hall door, and you can suck in 10,000 cubic feet of outdoor air in no time. People are opening and closing doors all the time.”

The doors must open for the service center to operate, so Lowe has no choice but to deal with humid air that was drawn into the ductwork. The result was that when the moisture condensed it provided an ideal environment  for bacteria - and that dirty sock smell.

When the problem cropped up recently in heat pump ductwork serving the facility and system adjustments could not cure it, Lowe sanitized the ducts by blowing in chlorine dioxide fungicide and deodorant into the air handler and throughout the supply ducts.

The dirty sock odor was gone. But work went on for Lowe and his Fluke meter. It’s a handy instrument for doing duct traverses to measure airflow, he said. He compares his real-time measurements against the design specifications on the building blueprints.

“I discovered the 975 meter from a flier Fluke sent me in the mail. After trying many different meters over the years and then seeing that the 975 had everything in one instrument, I had to get one,” Lowe said. “No need for a thermometer, ‘sling’ psychrometer, and CO/CO2 meter. No wetting sock material, no swinging a meter around, just push a button. Most CO (carbon monoxide) concerns are answered by the fire department. With the 975, there’s no need to wait for anyone.”

Monitoring airflow is crucial to ensuring air stays clean and healthy. Some tools, such as this meter from Fluke Corp. this unidentified HVAC technician is using, can check the air for carbon dioxide levels. Image courtesy of Fluke Corp.

On its own

Thanks to its toughness and ease of use, the Fluke 975 sometimes goes to work on its own.

“We actually ship that meter around to different service centers,” says Lowe. “If an occupant in someone else’s building reports a problem, that maintenance mechanic will let me know. I’ll put it in the ‘Pony Express,’ ship it to them, (and) they’ll use it and send it back.”

The meter’s simple operation makes it useful, even in the hands of nonprofessionals.

“You just turn it on and it’ll tell you what you need to know,” Lowe said.

Typically, the other mechanics find CO2 readings above 750 ppm. In some cases, their troubleshooting has uncovered a vehicle parked next to an intake, or a dry sewer trap “polluting” the air. Even an occupant with body odor can influence a building’s air.

In addition, the Fluke 975 brings with it an important element of credibility. Sometimes comfort issues initially blamed on poor indoor air quality are actually caused by light, noise or it could just all be imagined by the complaining occupant.

In these circumstances the Fluke  provides the real data that can lead to a solution.

“No one is willing to argue with a tester that is so big and technically sophisticated,” Lowe said. “It solves a lot of trouble. I mean, you bring that meter in there and the people look at it and they think you solved their entire life.”

This article was supplied by Fluke Corp.