When most people hear about open-air germ warfare tests at Dug-way Proving Ground, they envision airplanes dropping clouds of germs that could float off base _ like when a 1968 chemical arms accident killed 6,000 Skull Valley sheep.

While Dugway officials say such testing may have occurred decades ago, they have recently said that modern open air tests are much smaller _ more comparable to a farmer spraying pesticide from a tractor.

Instead of testing how germ clouds disperse over an enemy, the smaller tests evaluate germ detectors and decontamination systems.

In other words, the Army says modern open-air germ tests pose virtually no threat to residents living off the base and little threat to workers on base.

But it may not have always been that way. And judging current Army claims is difficult because it will release few documents about modern tests (see accompanying story).

Following is what little is known about tests through the years, pieced together through available documents, books and interviews.

Germ testing from 1945 to 1969 was designed to develop germ weapons for use in a retaliatory attack if another country used such arms first, and to evaluate defenses against such weapons, Army documents say.

Because tests were designed to develop weapons, they used some of the most dangerous germs known to man. Diseases they could cause include parrot fever, Q-fever, undu-lant fever, anthrax, tularemia, the plague and botulism.

Investigative reporter Charles Piller in an upcoming article in "The Nation" says Army documents he has obtained show at least 450 gallons of germ agents were disseminated in tests through 1969 _ and likely much more. That is significant because just one drop contains billions of organisms, and just one organism is enough in some cases to cause infection

To show the large amounts of germs that might have been used, Piller said just one test in 1958 dropped 40 gallons of deadly Q-fever slurry from an F-100A jet traveling near the speed of sound.

The first germ warfare test at Dug-way likely occurred in 1943 when a four-pound anthrax bomb was tested there, according to the recently released book "Gene Wars," by Piller and microbiologist Keith R. Yamamoto.

But Army lists of open-air germ tests provided to the Deseret News make no mention of it. The earliest open-air tests they mention were in 1945, and say a simulant _ rather than real disease-causing pathogens _ was used.

Information about procedures used in the tests of that period is sketchy, but interesting.

For example, Army officials say some germ warfare agents were mixed with dirt, placed in dishes and left in the open air near Granite Mountain at Dugway to test how long they would survive in desert conditions. They were covered with a screen to prevent disturbance, and the location was marked on maps to keep personnel away. They were not technically considered open-air tests because the agents were not flung into the air.

The Army told the Deseret News that it had tested several germ weapons by dropping or firing them from towers around the base. Piller said biologic bombs were also dropped from airplanes.

Piller also says documents released through the Freedom of Information Act say bombs filled with agent that causes undulant fever and other undisclosed organisms were dropped from 25,000 feet and set to detonate at 10,000 feet _ meaning they would have dispersed over a wide area.

Piller's and Yamamoto's "Gene Wars" also says, "At Dugway the Army apparently infected and released many species of animals. University of Utah researchers then conducted periodic assays to monitor the rate and extent to which the disease spread through the animal population. Despite Army denials, university contract reports indicate that infected insects may have been released as well."

But that recently brought a strong denial from Dugway spokeswoman Kathy Whitaker.

She told the Deseret News that the Army never infected and released any animals as far as anyone on base now knows. She said the university studies mentioned were to provide base-line information about the environment to make it possible to notice any changes caused by testing.

However, she said non-infected mosquitoes were apparently released to test travel patterns. Also, she said non-infected guinea pigs were also placed at locations where organisms were released to determine how they would be affected.

Also, Army lists say 21 "field tests" involving disease-causing germs were conducted in or around Dugway's animal exposure chamber. Further details of such tests are unavailable.

Commanders of Dugway during that early period, most of whom were chemical corps officers, also told the Deseret News in 1979 that they were given little information about biologic testing at their base.

Lt. Col. Donald Yanka, who commanded the post from 1950-52, also said in 1979 that he was told that only biologic simulants were used during his tenure. But Army lists show that pathogens _ including those that cause the diseases parrot fever and Q-fever _ were used in open-air tests at the time.

In 1969, an international treaty banned the use and storage of germ weapons, so germ tests were not conducted at Dugway again for years.

But testing began to gear up again, according to Army documents, after 1974 military intelligence reports said Egypt and the Soviet Union likely had or were capable of making germ weapons that could not be detected by American troops until soldiers began getting sick or even died.

So field detectors and systems to decontaminate germs were devised and tested at Dugway in relatively small-scale tests beginning again in 1978.

Dr. I. Gary Resnick, chief of the life sciences division at Dugway, provided some test plans that detailed some procedures planned for those tests. The Army said final test reports could not be located, however.

Several tests evaluated the XM19 germ detector and alarm. After lab tests showed it could detect a variety of real pathogens and simulants in the air, the Army devised field tests to see if it would work in battle conditions.

Plans called for a variety of smoke, dirt, fog and other obscur-ants to be sprayed along with simu-lants in open air to determine whether the detectors could still accurately find germ agents and set off alarms, according to Army reports.

Another series of trials evaluated the Particulate Agent Detection Systems (PADS). In those tests, germ sim-ulants were sprayed on grassy plots from a small pickup truck.

A day or two later, vehicles with the PADS equipment would drive over the grass. The driving would cause some of the simulants to become airborne again, and officials would monitor whether the PADS equipment could detect those germs.

The Army hoped PADS would help warn and protect troops crossing fields that had previously been contaminated by germ weapons.

In another modern test, the Army wanted to determine whether sodium hypochlorite might kill or neutralize germs dropped on troops. It sprayed simulants from a nozzle 10 feet above the ground through a mist of sodium hypochlorite. Detectors beyond that determined how many germs had been killed.

Other tests in the past decade also have evaluated a laser system to detect germs, a system to protect tanks from germ attacks and another biologic agent test kit. The Army has not provided detailed documents about those tests.

Resnick said the Army took special precautions to protect workers and the public during the modern tests. That included conducting tests at night and when wind was slow - conditions that make the spread of germs over long distances unlikely.

The Army also uses computer modeling to predict times when germs will spread the least, and conducts the tests then.

Workers also wore masks and other protective clothing, and in many tests were required to change clothes and shower when they left test sites.

Despite such precautions, some groups still insist that safety for people and the environment is a major problem at Army installations such as Dugway.