St. Louis Responding to reports of fires and explosions involving its oxygen regulators, Allied Healthcare Products is voluntarily recalling oxygen regulators sold under the Life Support Products brand.

Users, which include fire departments and emergency medical service units, can have the aluminum components in the recalled units' high-pressure chambers replaced with brass components at authorized service centers nationwide, company officials said. The company said it is working with the U.S. Food and Drug Administration, which is recommending no aluminum be used in oxygen regulators.

The manufacturer of respiratory therapy equipment and emergency medical products reported a net loss of $1.9 million, or a loss of 25 cents a share, for the second quarter of fiscal 1999 ended December 31, 1998. The loss, which includes a charge for a voluntary recall of the oxygen regulators, compares to a net loss of $6.7 million, or 86 cents a share, for the same quarter the previous year.

The company is aware of 16 fires over the last several years involving oxygen regulators from several different manufacturers, 10 of which involved one of Allied's LSP regulators, company officials said.

Fires and explosions can occur in the oxygen tanks, cylinder valves and regulators of high-pressure oxygen systems when in contact with contaminants such as hydrocarbons, metal shavings and even dust particles; during handling and maintenance; or when tanks are refilled with gas. Allied regulators make up about 60 percent of the oxygen regulator market, according to officials.

A trade-in program will be announced once the new regulators are available. The models subject to recall are the LSP 106, 270, 280, 370 and 735 series.

In May 1997, Allied recalled the LSP 270 Series regulators to add a bronze filter, but the company said it is now essential that the internal high-pressure parts be replaced as well. -M.L.