A complaint about faulty equipment in the methyl isocyanate unit at Union Carbide Corp.'s pesticide plant in Bhopal, India, was raised more than three years ago by a maintenance worker who was later killed when phosgene spilled on him while he was cleaning the same unit.

Carbide settled the Indian equivalent of a workmen's compensation suit in that death on Dec. 24, three weeks after a massive leak of methyl isocyanate (MIC) at the plant killed at least 2,000 people and injured 200,000 more.

An Indian board of inquiry concluded that the worker's death on Dec. 25, 1981, resulted from his panicky response to the spill, but that the company was negligent because it had not acted on his earlier complaint that the valve from which the deadly chemical leaked was in need of repair.

The amount of any compensation paid to the victim's family was not shown in documents acquired by The Washington Post. Tom Failla, a spokesman at Carbide headquarters in Danbury, Conn., said yesterday he could not determine the amount of settlement, if any, or whether its timing had been accelerated as a result of last month's tragedy.

Failla said he has "every reason to believe" that the valve in question was replaced, since it did not appear among corrective actions recommended in a May 1982 survey.

Failla said Carbide considers that the worker's death was caused not by MIC but by a spill of phosgene, which is used to make MIC, an intermediate compound in the manufacture of the pesticide Sevin.

The Indian government panel reported that the victim "had told his brother that even before the operation he had noticed that the valve in question was leaking and he had reported the mattter to higher authorities. Thus it is clear that the old valve was not replaced and due to this old valve the necessary inference is that phosgene gas was leaking at the time . . . . This could be and should have been detected . . . . This establishes negligence on the part of the management."

The worker, Ashraf Mohd. Khan, died when liquid phosgene spilled on him and two co-workers during a routine cleaning of the unit. The three men were wearing protective clothing, including rubber gloves and boots. After the spill, the men ran to a shower about 30 feet away. En route, Kahn ripped off his gas mask, thus inhaling the highly volatile phosgene, which by then had turned into a deadly gas.

The three men were treated at the plant dispensary, after which Kahn was transferred to a hospital's intensive care unit, where he died the next day. The other men "got splash on their trousers" but did not suffer permanent injuries, according to Carbide.

After an investigation that dragged on for nearly three years, the five-member Indian inquiry board -- officially known as the Ministry of Agriculture's directorate of plant protection, quarantine and storage -- reached two conclusions: that "had Kahn not taken out his mask which was supplying fresh air for respiration there would have been no chance of inhaling the toxic gas which caused his death," and that "the incident would have been avoided had the mechanical system been made fool-proof in all respects."

The company said the phosgene vaporizers are cleaned every two or three weeks, "with utmost care according to established procedures . . . which call for workmen to be always prepared for the unexpected, notwithstanding best preparation." It said all workers assigned to the cleaning process are "trained on likely hazards" and "use of protective appliances and action required in case of exposure."

It said Khan had cleaned the unit several times in the nearly two years he had been assigned to the unit and was a member of the plant fire and rescue squad trained in the use of respiratory equipment in toxic environments.

The inquiry committee met nine times, from Oct. 19, 1982, through last Dec. 21, before issuing its final report. The investigation was delayed largely because the key witness, one of Kahn's co-workers, now works in Calcutta and refused to make the trip to Bhopal until the government agreed to pay his expenses.