fter announcing that a police officer and two Health Department workers had been exposed to anthrax spores while investigating a confirmed case of the disease at the NBC offices, city officials hastened to say that they would change their investigative procedures.

But yesterday, bioterrorism experts said that no unusual precautions are recommended for suspected anthrax contamination.

The Health Department lab technicians, who according to officials were wearing protective masks, gloves and gowns, actually exceeded the safety standards recommended by the the federal Centers for Disease Control and Prevention for a laboratory setting. The C.D.C. recommends biosafety Level 2, on a scale of up to four, in testing for anthrax — the same level it recommends for salmonella. Level 3 sometimes requires a respirator; Level 2 does not.

If anything, said Terri Rebmann, an infectious disease specialist with the Center for the Study of Bioterrorism and Emerging Infections at St. Louis University, the new anthrax exposures show how protocol will necessarily change as law enforcement and health officials gain more practical knowledge.

"Did he smell it? Did he put it to his face?" she asked about the police officer, who was not wearing gloves when he handled a suspicious envelope that later turned out to be contaminated. "We need to find out exactly, if we can, how that happened, because that would tell us a lot about how it's transmitted. Right now our basic training says it can't be spread from hand to hand."

There have been no other reported incidents of exposure of officials or medical personnel involved in anthrax investigations in New York, Nevada, or Florida.

For law enforcement, training and advice about hazardous substances come from a variety of sources, like the F.B.I., the Department of Justice, and the so-called Blue Book, or the Medical Management of Biological Casualties Handbook, issued by the United States Army Medical Research Institute of Infectious Diseases.

For anthrax, the Blue Book recommends standard precautions, like those that might be used by a medic taking a patient's blood, not safety measures used with contagious airborne diseases like tuberculosis.

But law enforcement officials tend to use greater safety measures, especially when entering a situation where not much information is available. Yesterday, specially trained firefighters in San Jose, Calif., suited up and donned masks and gloves before entering an airplane where a mysterious powder had been seen. It turned out to be confetti.

But it could have been anything, said David Huseman, an advanced life support education coordinator for the San Jose Fire Department, where officers have been trained to respond to weapons of mass destruction, such as biohazards, since the F.B.I. warned that the Bay Area was the third-most-likely target for terrorist attacks several years ago.

"If you don't get concrete information of what you're dealing with, you're going to go with the highest level of protection," Mr. Huseman said.

The fact that investigators in New York knew that a case of anthrax had been confirmed should have made them even more cautious, Mr. Huseman said. "That's like walking into a burning building without your fire protection gear."

But Mayor Rudolph W. Giuliani said at yesterday's news conference that adequate precautions had been taken at NBC. "A balance has to be struck here between sufficient precautions and making people so frightened and so upset that they're not going to be able to conduct their lives, which means having people walking around in spacesuits all over the city of New York," he said. "The reality is that I think they balanced that correctly."

Mr. Huseman agreed that bioterrorist threats are so new that there is as yet no clear division between appropriate action and overreaction.

"It's kind of like when H.I.V. and AIDS became a problem," he said. "People became very paranoid, and people reacted and responded in a certain way, and you need to change that through education."