Is c. diff contagious through airborne?

Definitely not: C. diff is a disease transmitted by the 'fecal-oral' route, which sounds disgusting because it is. Spores from another patient can contaminate the environment that someone might have visited earlier (like a shared bathroom in a 2 bed room in a hospital). Once those are ingested, under certain conditions (antibiotic use mostly), the spores can germinate and cause infection. C. diff can be bad news.