Infrared Photography Help
"That's strange. If the film is in a cartridge like all other 35mm films, why will it fog in normal light?"...........
I shot IR film for over 15 years, and in fact it was my main film! Light will leak past the canister opening and IR film is much more sensitive to light ingress.
“A real IR filter looks completely black to the human eye.”……….
It's not very likely the person will want to use more than the R25 filter.
For the OP, make sure your friend reads up on IR film handling and usage! It's a wonderful and interesting media.