ROCKTON, Ill. (WTVO) — Questions regarding how air quality is being monitored continue after the Monday Chemtool fire in Rockton.

We caught up with an Environmental Protection Agency official to get an up-close look at how these different devices work.

He tells us some collect air samples using a vacuum and that data is then sent to a lab

“This chamber here has a vacuum in it and then as we open up the valve, this device right here is the flow controller and it controls how fast the air comes in,” said Matt Villicana of the EPA.

Villicana is a federal United States on-scene coordinator for the EPA.

“Our mission here is to do the air monitoring, collect the air samples to make sure that the citizens around the area are not being exposed to any toxic vapors, particulate matter that may have been released by the smoke,” he explained.

In order to do that, he says they use machines like the dust track–which looks for particulate matter in the air.

“We’re looking for primarily what’s called PM10 and PM2.5 and those are sizes of particles that are restorable – so PM10 tends to lodge in the upper airway and upper lungs and PM2.5 lodges deeper in the lungs,” said to get an up-close look at how these different devices work,” said Villicana.

They also tested for toxic gases as well.

“[We searched for] hydrogen cyanide, hydrogen sulfide, volatile organic compounds because those are most prevalent usually in a fire at a facility like this.”

He tells us the results have stayed consistent.

“Especially now that we’re only dealing with the occasional flare-ups – we believe there are no unknowns that we’re dealing with,” said Villicana.

Residents continue to express concerns about the accuracy of the monitors, but Villicana explains how that is measured.

“These are all very accurate. Most of the monitors are calibrated daily, compared to known amounts of specific gases so that they can make sure that their accuracy is in a range that is deemed appropriate by the manufacturer.”

The EPA is posting updates on the Chemtool fire here.