Joan Bendel and Ed Lewkowicz look like characters out of a low-budget science fiction movie.

	Bob Donaldson, Post-Gazette
	Walking at a brisk pace on a treadmill, Rod Salka wears a new respirator model connected with a model air pack during the device's testing at the National Institute of Occupational Safety and Health research facility in South Park. Click photo for larger image.

Encased in a 10-foot by 10-foot metal box, the waitress from Elizabeth and the Monroeville police officer are wearing black respirator masks that filter clean air and seal their noses and mouths from the isoamyl acetate being pumped into the dimly lit chamber.

As technicians peer through the box's window, the bemasked Ms. Bendel and Officer Lewkowicz wiggle their heads from side to side and up and down, then stretch out their arms at shoulder height and begin rotating them. Eventually, they start jogging in place and pumping up and down on a bicycle pump.

They're not being tested. Rather, they are testing the respirators they are wearing to determine if any of their movements cause the scent of isoamyl acetate -- banana oil that smells like a truckload of banana popsicles -- to sift through.

"If for any reason they smell banana oil, they'll stop what they're doing and put their thumbs down," says Pat Wiltanger, an engineering technician observing the test subjects at the National Personal Protective Technology Laboratory in South Park.

The lab, which is part of the National Institute for Occupational Safety and Health, was established in 2001, largely in the wake of the Sept. 11 terrorist attacks. It certifies that respirators used by fire and rescue personnel, miners, health-care workers and others provide the protection manufacturers say they do.

U.S. customers purchase an estimated $2 billion of respirators each year. The devices can be as basic as a mask that protects a worker from dust particles to sophisticated four-hour units used to rescue trapped coal miners.

Depending on the demands of the job, a typical respirator must pass from three to 29 out of 150 possible tests performed at the lab. Humans can't be used for some of the testing because it involves substances that are IDLH -- industry lingo for "immediately dangerous to life and health."

But when banana oil, corn oil or some other harmless substance can do the job, lab director Les Boord relies on a stable of about five dozen civilian guinea pigs.

Ms. Bendel, 46, a single mother of two, supplements her Red Lobster paychecks with one or two tests at the lab each month. The pay, which varies based on the test, doesn't compare to winning the lottery, "But every little bit helps," she says.

Mr. Lewkowicz, 39, says some of the money he receives goes toward gasoline to get to and from the Cochran Mill Road facility. For him, the testing is more personal. As a member of Monroeville's volunteer fire department, he eventually may use the equipment once it's certified.

Like many test subjects, Mr. Lewkowicz heard about the job by word of mouth. Volunteers must be between 18 and 50 years of age and pass a rigorous annual physical that includes vision and hearing testing, blood work, an electrocardiogram and, for those over 40, a stress test.

The most unpleasant aspect of the banana oil test -- which pays $50 -- is smelling like a banana for an hour or so afterwards, says engineering technician Eric Welsh. He says the "cold test," climbing into a minus 25 Fahrenheit chamber to determine whether a respirator works in a frigid environment, leaves some subjects with the same headache they get by eating ice cream too fast. For that, they get $75.

Then there's the "man" test, apparently named pre-women's liberation. Each subject straps a harness containing a 30-pound carbon fiber oxygen tank on his or her back and connects the tank to a respirator that fits snugly over nose and mouth. Then, depending on whom the respirator is designed for, the subject can go as little as 30 minutes on a treadmill or endure a grueling four-hour circuit of exercises: the treadmill, climbing stairs, using a pulley to lift a 45-pound weight 8 feet, and carrying a 50-pound bag of sand up a 16-foot catwalk and bringing it back down again.

"They earn their money, the subjects who do this. It's not easy," says Heinz Ahlers, acting chief of the lab's respirator branch.

Manufacturers run many of the same tests on their respirators before submitting them to the NIOSH lab.

"The [NIOSH] tests are very expensive if you don't pass, so we want to have a very high confidence level that we have something that is going to pass," says George Blank, manager of protection products for Draeger Safety in Findlay.

MSA does a slightly different version of the banana oil test to determine how much of the substance leaks inside the mask. Ken Bobetich, group manager of industrial protection products for the O'Hara firm, says some humans can't detect the sweet smell on their own. So MSA's test measures the concentration of banana oil inside and outside the mask.

"We prefer to have hard numbers," Mr. Bobetich says. "The key to respiratory protection is fit. If you have the best filter but the mask doesn't fit you correctly, there is really a degradation of performance."

How well a respirator fits depends on the size of the user's nose, mouth and other facial features. Based on recent scans of 3,400 human heads, NIOSH hopes to help the industry produce "designer" respirators fitted to the size of the user.

"That's really what you'd like to be able to do long term," says Ronald E. Shaffer, chief of the lab's research branch.

Until then, Ms. Bendel, Mr. Lewkowicz and others will be on call.