Nearly every evening, Carolina Simmonds drives out to the country to take a deep breath.

Instead of paying attention to the wildflowers or the wheat swaying around her, Simmonds sniffs for manure and the myriad of gases released as organic material decays.

Simmonds, who works for the Idaho Department of Agriculture, monitors dairy odor levels as part of an effort to develop standards that both dairies and their neighbors can live with.

When she finds a particularly foul spot, she writes down what she smells and waits for a reading from the Jerome Meter, an electronic nose that measures the concentration of hydrogen sulfide compounds -- the gas that makes up much of the stink rising from cow patties and sewage lagoons.

The dairy industry has strongly opposed the establishment of standards for levels of hydrogen sulfide or other gases. They say that in today's fragile economy any deodorizing solution is likely to be too expensive. Meanwhile, neighbors say they are losing property value because of the odors.

Dean Swager, who milks about 1,900 cows and recently bought a dissolved-air flotation system to cut the odor from his farm, said odor standards sound fine, except that they don't take into account geographical factors that can affect the distribution of odor. Air flow and climate patterns sometimes dissipate smelly gases, but they sometimes trap the stench close to the ground, too.

Matthew Thompson, the head of the technical support division of the odor program, said the professional sniffers will soon use more than just the Jerome Meter and their noses.

The department is looking into olfactometry -- a process that uses a trained human nose and air samples divided into different concentrations of smell intensity.

"Basically, you pour a sample of air into a bag and take it to a special lab, where they run samples of the dirty air with a high volume of clean air," said Thompson. "Then a group of people are given three choices: two clean air samples and a diluted dirty air sample, and they're asked to choose the dirty one."

The dirty air sample is mixed with less and less clean air until the professional sniffers detect a difference between it and an entirely clean sample. Thompson said the system is the best way to measure scent because noses are the most accurate measuring devices available under current technology.

Simmonds said that every nose is different, but that her sense of smell sometimes differs with what the Jerome Meter reads. To account for varying levels of measurable hydrogen sulfide and their impact on a human being, she writes down her own impression. The smell journal reads almost like a wine critique.

"Here I smell strong ammonia, and something kind of acidy," she said outside one dairy. "And when we were around the corner, I could mainly smell manure."

Which is the last thing nearby residents want to smell when they are hosting a backyard barbecue or patio party, said Simmonds.