anti-virus programs

Hello. I want to scan the BIOS for viruses, but i don't know how to do it. This is the BIOS: Brand: Phoenix Technologies Ltd. Version: V1.09 -AMD AGESA StoneyPI V1.3.0.G I need to see if there are viruses in the BIOS. I'm not aware of any anti-virus program that can scan the BIOS. After all...

Do anti-virus programs introduce changes to the files they scan, or do they only read them, meaning it's impossible for an antivirus program to change/corrupt files? For example, if the system crashes or the anti-virus app crashes while scanning a file, could the file become corrupted? If the...