FAIRBANKS, Alaska — A cluster of school buses coughs diesel exhaust in the parking lot of Randy Smith Middle School on a bitter cold December day.

Nicole Swensgardi raises her eyebrows and turns into the parking lot. She is on the hunt for air pollution.

The 30-year-old data collection technician is driving an unmarked newer-model Ford Escape with a funny-looking antennae sticking out of a back passenger window. It's not an antennae exactly. It's a pollution detector, or sniffer, as Swensgardi and some of her co-workers at the Fairbanks North Star Borough air quality office call it.

The vehicle provides real-time measurements of a harmful pollutant known as PM 2.5, tiny particulate matter that is belched out of chimney stacks and exhaust pipes and lingers when the air is cold. The pollutant cannot be seen with the naked eye. It's about 28 times smaller than a human hair, which is what makes it so dangerous. Its minuscule size means it can lodge deep in the lungs. Studies show that over time it can make people sick.

A black box, about the size of a mail box, rests inside the Ford on the center console providing the PM 2.5 measurements, taken in micrograms per cubic meter of air. Swensgardi will later combine the PM 2.5 numbers with GPS and temperature information so she can map the pollution.

"We can see which areas of town are good and which are unhealthy," she said.

As Swensgardi loops around the middle school parking lot and past the buses, she scrunches her nose says she is getting a "bump."

"Yuck, diesel," she said.

Swensgardi left the middle school, turned onto the Johansen Expressway and pointed to a business nearby that heats by burning pallets.

"We usually get a spike from them," she said, "and the train, of course," she added, nodding toward the railroad yard below.

Swensgardi headed toward the Watershed School in the neighborhood across from the Fairbanks International Airport, a pollution hot spot because of the amount of wood burning.

The numbers on the black box double, though they are still in the realm of what is considered decent air.

The next stop is across the Chena River at the Woodriver Elementary School. The borough is keeping an eye on the pollution there after numerous complaints.

Two homes across from the school have outdoor wood boilers. Some outdoor boilers are known to put out dense smoke.

On this day, one was putting out smoke that looks no different than neighboring chimneys. No smoke came from the smokestack of the second outdoor wood boiler a few doors down.

Swensgardi and her co-workers call the Ford the Sniffermobile. While it's handy, it's not the official means the borough uses to monitor air pollution for the purpose of complying with the federal Clean Air Act.

Official measurements are taken hourly from pollution detectors in downtown Fairbanks and in North Pole. Those numbers, averaged over 24 hours, help the borough determine whether to issue an air quality advisory, when people are warned to limit activity and take steps to mitigate the pollution.

The Sniffermobile is used when people call with pollution complaints. It measures the PM 2.5 of the alleged polluter. In some cases, photographs are taken, and the information is put on file.

"It's totally legal," Swensgardi said. "We are allowed to sit at the end of someone's driveway."

In most cases, the borough has no power to take punitive action against polluters. New rules on chimney smoke opacity kick in next winter, but the rules are expected to be rolled back by the Borough Assembly in light of a successful ballot proposition prohibiting the borough from regulating how people heat their homes.

Once, last winter, Swensgardi was measuring PM 2.5 at Dawson Road and Lineman Avenue in North Pole and the number soared into the thousands. More than 100 micrograms means the air is bad. A thousand micrograms is horrendous.

Swensgardi said it made her feel sick.

"Sometimes, when I drive around and I see people riding their bikes, it concerns me," she said. "I want to pull over and tell them, 'Hey, the air is unhealthy right now.' I am way more aware than anyone else because I have got the machine in my car."

Information from: Fairbanks Daily News-Miner, http://www.newsminer.com