biohazardous blood does not have to be ingested in order for someone to become exposed! it can enter through your skin through an opening such as a papercut. or better yet, any skin that is open, this includes dry, ashy skin, or any scratch on your skin that makes your skin white. and human HIV is transmitted through bodily fluids dude! you don't have to eat it to get exposed lol. it's an STD, you don't have to eat to get an STD. i can't remember how exactly how long HIV can remain potentially dangerous in blood on a car, but there's lots of other diseases like Hepatitis, which can survive a very long time, i can't remember exactly either. but yea, it's better to be safe than sorry, seriously.