Researchers working with infectious diseases must always be cautious when conducting experiments, and such caution is carried to extremes in the laboratories at Harvard's Center for Clinical Research on AIDS.

Professor of Medicine Jerome E. Groopman, who co-directs the Center, has two labs for two different kinds of research--one for studying and testing blood samples, the other for working with cells and viruses. Each is named for the level of precaution required for work--Biosafety Level 2 (BL-2), for work with the blood samples, and the high-caution Biosafety Level 3 (BL-3), for work with the cells and viruses.

In either lab, researchers must conduct their work inside a large box called a liminer flow hood. Since the blood sample under study may contain the AIDS virus or the more infectious hepatitis virus, researchers must put their hands through an opening in the hood to make sure all dangerous particles are contained within.

The scientists wear two pairs of rubber gloves while conducting experiments, but the hood provides an extra measure of safety by placing a downward flowing air current between the researcher and the samples. Thus, if any particle came floating toward the scientist, the current of air would push it down to a filter at the hood's bottom, preventing it from ever reaching the scientist.

When finished working in the hood, researchers must remove their outer pair of gloves and put them into a sterilizing machine called an autoclave. From there, waste goes into a bag that is periodically sent to a special site for incineration of laboratory waste.

All these safety precautions are much more than is necessary, says Randal A. Byrn, an instructor in medicine who works in Groopman's lab. But "because of [the nature of] our work, we take it real seriously," he says.

And the extra precautions are costly. Byrn says that a pair of gloves costs about 40 cents, and spending a day in the lab, a researcher may go through 10 or 20 pair.

Even more safety precautions lie within the BL-3, which is accessible only through the BL-2. Air is constantly filtered through the BL-3 room into ceiling vents to prevent the release of harmful chemicals. In addition, all equipment in the BL-3 is wiped with alcohol immediately after use, just in case any microscopic particles might remain on the surface.

In the BL-3, many of the most vital experiments--the ones involving immune cells and the AIDS virus--are conducted. The lab has an incubator where cells can be "grown," and all work there is also done in hoods.

Of course, such stringent safety requirements can make a researcher's life difficult. Nothing can be removed from the BL-3, not even the papers scientists write their data on.

So in order to make use of experimental data after tests have been conducted, Groopman's team must fax the data from their lab to their office--which is just down the hall--and dispose of the original unsanitary paper with the other waste.