The companies have been seeking for years to get Congress to pass legislation giving them immunity from liability lawsuits, including in a current bill to authorize about $8 billion to be spent on coronavirus readiness.
The bill, approved Thursday, didn't include the provision. Democratic congressional staffers said their concern about such a provision is that it would be too broad and cover a too-big range of products. .
The issue is that there are two basic kinds of N95 masks, and makers say they each have a different legal status. One is the type of masks that often are used in hospitals and often are cleared by the Food and Drug Administration.
The other type, commonly used in mining and construction work, is approved by the National Institute for Occupational Safety and Health (NIOSH). The first type gives the manufacturers immunity from liability under federal law; the second doesn't, lawyers say.
The problem in the current coronavirus outbreak is that many paramedics and other emergency responders could often be wearing the second type of mask, which protects them against disease -- but not necessarily against legal liability.
"There is a vast supply of N95 masks in the industrial setting," said Charles Johnson, president of the International Safety Equipment Association, makers of masks, hardhats and other protective gear. "All of these are protecting medical and first responders."
Mr. Johnson said the vast majority of such N95 masks don't have FDA clearance.
Now, at a time the U.S. could run short of masks because of demand from medical workers and the general public, Mr. Johnson said the NIOSH process is rigorous and that "we're trying to get a larger supply to medical personnel."
Over the weekend, Vice President Mike Pence said there are currently about 40 million masks nationwide and the government is seeking to increase the nation's supply by as many as 35 million each month.
On Thursday, Mr. Pence and FDA Commissioner Stephen M. Hahn visited 3M Co. of St. Paul, Minn., the nation's leading maker of N95 masks.
Mr. Pence said the administration would work with Congress on extending legal protections for mask manufacturers in case people get sick.
Asked about concern over a mask shortage, Mr. Pence replied that the U.S. is prepared now, "but we want to be ready tomorrow. As we are expanding testing around the country there are going to be more cases. We're going to find more Americans have contracted the coronavirus."