Federal scientists promised this week to use converted germ war laboratores at Ft. Detrick to prove safely the "revolutionary" value of experiments that make new forms of life by mixing genes.

They won the support of two members of the Frederick County board of commissioners, including acting chairman paul Crum, for new genetic research facilities at the former Army base. The base is now largely the Frederick research center of the National institutes of Health.

But commissioner Donald Lewis of Thurmont called for a mortatorium on such a search until "it's looked at very closely." He said "there is apprehension of people in Frederick County, looking back to germ warfare," and said he would propose that the commission hold a public forum to hear both scientist and objectors.

"I haven't seen any groundswell of opposition," Crum replied. "I'm for doing this research subject to careful controls." Commissioner Edgar Virts, a livestock breeder, agreed.

The three spoke in interviews after NIH scientists spent two hours telling Frederick and Montgomery County officials of plans for the new research at Frederick and on the NIH campus in Bethesda.

About 75 persons attended an "informational meeting" at NIH. When the scientists finished, they asked for questions or comments from invited officials or the public. There were none, in contrast to fieree opposition to the research in some cities.

Dr. Donald Fredickson, the NIH director, opened the meeting by pleding that NIH - in Bethesda or Frederick - will remain "an open community," with "nothing that cannot stand maximum public scrutiny."

"We have no secret research here," he said. "We never want the mandate of responsibility to conduct any." Then he and others told how NIH will starts by June to operate two "P4" laboratories, lahs to house genetic experiments with highest potential risk, at NIH and a third at Ft. Detrick.

By the summer of 1979, these will be followed by a large National Recombinant-DNA Facility at Detrick, the result of a $3 million remodeling of three building to keep any possibly dangerous new organisms inside laboratory walls.

DNA (deoxyribonucleic acid) is the stuff of the genes of virtually all living things. Scientists have learned to join the DNA of almost any two forms, though they are so far making such "recombinants" mainly by injecting DNA - from mammals, algae or microbes - into colonies of bacteria that then act as hosts into which new hybrid DNA can be grown at will.

NIH scientists said their priority will be many "safety experiments" to try to make sure such research will not create new diseased organisms or poisons that might spread. NIH guidelines now forbid certain types of experiments entirely because of such unknowns.