Researchers Working to Establish an Odor Index

May 8 -- It's little wonder that scientists are obsessed with numbers, since so much of their work relies on measuring and quantifying. They've got a number for just about everything.

Light is measured in candelas. Sound in decibels. If you're running a pneumatic drill, chances are you're generating 80 decibels of ear-piercing noise.

But ask a scientist how bad the pig farm down the road smells, and you'll probably get a quizzical look and a vague answer. When it comes down to odor, the nose knows when something stinks, but there's no olfactory equivalent to decibels.

So along comes Seth Hapner, who is finishing up his master's degree in environmental engineering at Penn State, with a possible solution to this dilemma. Hapner, along with Bradley A. Striebig, who heads the environmental technology group at Penn State's Applied Research Laboratory, has developed what he calls an "odor index."

Current Meters Too Subjective

He used off-the-shelf technology to create an instrument-based system that can detect gases given off by any substance and in what quantities, and then put a number on it. If the odor index value is 1,000, you should be able to detect it. If the index is 10,000, and the chemical is hydrogen sulfide, you should just be able to detect the fine scent of rotten eggs. And if it's 100,000, you'll want to plug your nose and get the heck out of there.

The most commonly used system today involves submitting air samples to various labs around the country that have "odor panels." If an environmental engineer wants to know how bad something smells, he or she can submit a sample, and the folks who serve on the odor panel will take a sniff and render up their judgment. (And you thought you had it bad.)

The problem with that system, Hapner says, is it's very subjective, despite efforts by the labs to get reliable people to serve on the panels.

"We're trying to come up with a method that would be repeatable in any lab around the country," Hapner says.