Kaleida Health now requires all staff members to wear procedural/surgical masks when they are within six feet of any patient or another staff member.
Kaleida said its "universal masking" requirement applies to vendors and other visitors, too.
Niagara Falls Memorial Medical Center said it intended to institute the same requirement today.
Surgical masks aren't as protective as the N95 respirator masks that are in short supply, but they do provide some protection.
According to the Food and Drug Administration website, an N95 mask is "designed to achieve a very close facial fit and very efficient filtration of airborne particles."
A surgical mask tends to be loose-fitting, depending on the design.
"It does not filter or block very small particles in the air that may be transmitted by coughs, sneezes or certain medical procedures," the FDA website says.
The Covid-19 virus is transmitted primarily through the air, although it can also live on surfaces.
Kaleida Health said it continues to screen all individuals that enter its facilities through designated and limited access points. This includes mandatory temperature screening, and now, mask education and instructions.
At Erie County Medical Center, spokesman Peter K. Cutler said workers must wear the N95 when dealing with Covid-19 patients, but whether they wear masks elsewhere is up to them.
Both Cutler and Kaleida Senior Vice President Michael P. Hughes said their hospitals have about a week and a half to three weeks' supply of personal protective equipment, which includes N95 masks, gloves and gowns.
"We have inventory, but it's very limited," Cutler said.
He said the hospitals are working with U.S. and foreign suppliers to find more personal protective equipment.