Look, your friend is using them, maybe you want to ask him if it's "hot" or not. I'm trying desperately to remember whether it reduces the "heat" of the smoke, and if it does, I'm betting that is not good. Because it actually means the smoke is being affected by the plastic, somehow, cooled, and that usually means it's interacting with the plastic somehow.
All I remember is what they tasted like. Maybe your "friend" can come here and ask about them, if he's not concerned about his health, I don't really see why you should be. If you want to find out more, well I just searched, and granted this is not my typical source, but sheesh, there has been NO safety data on those things. BUT here is a yahoo answers link where a variety of folks chime in on whether they are "safe" or not.
I should by all rights point out that the filters NOW STANDARD on all cigarettes did not reduce mortality rates a WHIT. So it appears. You may filter something, but until you filter it to the point that any and all SMOKE is filtered out, you will still be combusting tobacco.
That is, emphatically, and by all KNOWN MEASURES unsafe, and if the plastic tips did anything, there would have been peer reviewed studies or whatnot. My thoughts are the folks using them found tobacco more disgusting, and/or smoked less. Or, it was a placebo effect.
But have at the link:
Do TarBlock Cigarette Filters really work?
I think they're either meaningless, unsafe, or both.
I am still asking what this has to do with vaping. Are you trying to get your friend to vape, well, okay, explain to your friend that there is NO safety data at all regarding the plastic filters. It's all either anecdotes, or nonsense, or both.
Anna