Clues and why testing is the only proof
You usually cannot tell whether a material contains asbestos just by looking at it. The only reliable way to confirm asbestos is laboratory testing of a small sample taken safely by a trained professional.
That said, there are clues. The biggest is the building's age — homes built before 1980 are more likely to contain asbestos materials. Suspect items include popcorn ceilings, old vinyl floor tiles, insulation wrapped around pipes and old heaters, and certain textured walls.
You should not try to collect a test sample yourself, because breaking off a piece can release the very fibers you are worried about. Professional asbestos inspectors know how to sample safely and have the material tested by a certified lab.
If you suspect asbestos, the safest approach is to leave the material alone and avoid disturbing it while you sort out testing and responsibility. If you are concerned about possible asbestos in your rental and unsure who should pay for testing, a free, confidential review can help you understand your options.
This is general information about California tenant rights, not legal advice. Every situation is different.