I know this is an old thread but I recently got an bad infection in my leg. I blame these things. It’s the first time I used them. There is no valve that closes off the bottle to the air when u remove the barrel. Why idk as they are on almost every quick connect medical device I’ve had the pleasure of being hooked to. I tried leaving a barrel hooked to them when not in use to keep them clean. However it’s very hard to be sure all bacteria is removed from something that has so many hiding places. It’s too bad i really liked the idea of not wasting a needle on the stopper. In the past I have also reused the same needle to draw every time. I never had any trouble but it’s not really worth the $0.25 and that’s my $0.02.