What is the test for a fireman's rule?

"The fireman's rule is primarily based on the principle of law denominated assumption of risk. That principle holds that 'one who has knowingly and voluntarily confronted a hazard cannot recover for injuries sustained thereby.' " (Lipson v. Superior Court (1982) 31 Cal.3d 362, 370, 182 Cal.Rptr. 629, 644 P.2d 822.) "As many other jurisdictions and legal commentators have recognized, a fireman does not assume every possible risk he may encounter while engaged in his occupation. [Citations.] A fireman assumes only those hazards which are known or can reasonably be anticipated at the site of the fire." (Id. at p. 371, 182 Cal.Rptr. 629, 644 P.2d 822.)