Never use a kerosene heater in a tightly sealed room.

Never go to sleep with the heater still operating.

Never add fuel when the heater is on or hot.

These are three of the safety rules consumers should follow to avoid hazards associated with kerosene heaters, which have soared in popularity in recent years and now are used in millions of American homes as supplemental and even primary heating. An estimated 3 million kerosene heaters were sold in 1981, and an estimated 10 million may be in use by the end of the present heating season.

Consumers like the heater for two reasons: It provides a comfortable source of heat, and it holds the promise of savings on energy bills. Those savings supposedly result when consumers turn down the thermostat on their central heating units while using the small heaters to keep living quarters warm.

But as the popularity of the units has soared, so have questions about their safety.

Just last week, the Consumer Product Safety Commission reported that preliminary research showed emissions from certain kerosene heaters caused air pollution levels significantly higher than government health standards. The emissions are high enough to cause breathing problems and changes in heart rhythm for some consumers, the CPSC said.

Final results from the agency's research won't be available until June.

At that time, the agency also will address other concerns about kerosene heaters, such as burns resulting from contact with hot surfaces on the heater, fuel leakage, use of the wrong fuel and problems with adjustment and maintenance of wicks.

Industry and consumer groups are taking an active role in the kerosene-heater safety controversy. Last October, Consumer Reports magazine published an article recommending against the purchase of heaters because of the fire hazard and the emissions. Kero-Sun Inc., the largest distributor of kerosene heaters, with 35 percent of the market, promptly filed a $51 million lawsuit against the magazine. That case is pending.

Meanwhile, the National Kerosene Heater Association, a trade group, has paid outside consultants to conduct a series of tests on kerosene heater safety. Industry representatives have concluded that heater emissions are within government standards when the machines are operated safely.

Officials from industry, government and consumer groups say their test results vary because of basic differences in the amount of ventilation in the model used.

But CPSC Chairman Nancy Harvey Steorts contends that "the jury is still out" on the question of safety. Until the government completes its work this spring, she said, there is no way to know for sure what risk heaters pose for consumers.

To get that message out to kerosene heater users, the CPSC is working with industry and fire safety officials on special announcements and publications. The International Society of Fire Service Instructors, a professional organization, has produced a series of 30-second television spots that has been distributed to 250 cities, including the Washington metropolitan area. Those messages began appearing on local television in late January.

In addition, the National Kerosene Heaters Association has published information on the safe use of kerosene heaters telling consumers what they should and should not do. That includes:

* Always buy and use only uncontaminated, water-clear kerosene, such as Grade 1-K or its equivalent. Never use gasoline or any fuel other than kerosene.

* Always store kerosene in a clean, tightly sealed metal container clearly marked "kerosene."

* Always refuel the heater outside the living area.

* Always extinguish the heater before sleeping. Never leave it unattended while in use.

Finally, the CPSC has issued a special bulletin on kerosene heaters explaining the risks and how consumers can minimize those risks. The bulletin also offers basic suggestions on the selection and use of a kerosene heater.

A copy of the bulletin can be obtained by writing the U.S. Consumer Product Safety Commission, Washington, D.C., 20207. Ask for "Kerosene Heaters."