For the study at the University of California, Los Angeles, 54 people who work in a building were asked if they knew the location of the fire extinguisher nearest their office.
Although many of the participants had worked in their offices in the building for years and had passed a number of the bright red extinguishers several times a day, 24 percent knew their locations.
Yet when asked to find a fire extinguisher, researchers found, everyone was able to do so within a few seconds, with most of the participants saying they were surprised they had never noticed them.
"Just because we've seen something many times doesn't mean we remember it or even notice it," UCLA psychology Professor Alan Castel said.
Not noticing things isn't necessarily bad, he said, particularly when those things are not important in your daily life.
"It might be a good thing not to burden your memory with information that is not relevant to you," he said.
But safety information, like knowing where fire extinguishers are or what to do in an emergency, could be vital, he said.
"We don't notice something if we're attending to something else," Castel said. "Fire extinguishers are bright red and very conspicuous, but we're almost blind to them until they become relevant."