The speed, skill, and legendary bravery of urban firefighters is so taken for granted that a decision made at the Hilton Hotel fire last weekend came as a shock. For the first time in our memory, city firefighters waited two hours before before entering a burning building. Although no lives were at risk and the hotel's management says the fire was under control at all times, the fire department's hesitation serves warning that better planning is needed if a future catastrophe is to be averted.

PCBs are the problem. Polychlorinated byphenyls are organic compounds produced in the United States between 1929 and 1977. Because of their fire-retardant properties, they were used as coolants for electrical transformers. But when PCBs burn, they release extremely dangerous chemicals that seep through the skin and even contaminate substances as dense as concrete. The chemical fumes pose severe health risks and may cause cancer, liver damage, sterility and birth defects.

Of course, no one wants firefighters exposed to this hazard, and it is prudent policy for them to refuse to enter a building -- where life is not threatened -- until they know whether the danger of PCBs is present. But of equal concern is the threat to public safety when firefighting is hindered.

Some steps can be taken right away. The fire department knows which government buildings have old PCB-cooled transformers, but it has no data on privately owned buildings. A rule published this month by the Environmental Protection Agency requires that local fire departments be notified, by December, of the location of each of the 140,000 PCB transformers in the country. That's too long to wait. Notification should be accomplished on a voluntary basis without delay, so that fires in structures that do not pose a danger -- like the Hilton Hotel -- can be fought immediately. Pepco, real estate interests and insurers -- who have a great deal at stake -- should cooperate in getting the information together and getting it into the hands of the city's fire department.

What should be done, then, about the buildings that do have the hazardous substance in their transformers? The EPA, after six years of proposed rules and extensive litigation, has now ordered that such transformers in commercial buildings must be replaced or modified by 1990, but that's not good enough.

The rule should cover all hazardous transformers and the timetable should be advanced. PCB fires have already occurred in Miami, San Francisco, Chicago and Binghamton, N.Y., and the dollar losses due to contamination have been staggering. The regulators must move more quickly before a major fire involving these deadly fumes exacts a higher cost in human life.