Tube smell?


Some 5687 tubes I just installed have a mild but definite
burning-rubber odor. It's not extreme, but it is there
if you sniff around them (and I can also detect it around
the room). Has anyone ever had this? Could it be something
oxidizing because they are newly installed?

It's a bit hard to tell, but it seems to be all 4 of them,
not just one.

The tubes work fine, but look brighter than
my old cheaper 5687s. They sound absolutely great,
nice and smooth and mellow.

It's not the amp, as the old tubes don't smell.

Thanks for any help.
rgs92
I just put a fresh quad of Shuguang KT88-98 tubes in my VAC amps and for the first 8 hours or so, they had a distinctive odor to them. The odor gradually faded away.
Is the smell matched? ;>). Only kidding, Don't risk creating a problem, get rid of them pronto, only bicycle tubes are supposed to smell like rubber.
I've always thought "tube smell" was dust burning off. I enjoy the tube smell from my vintage gear.
The aroma disappeard after a day or two.
Thanks for everyone's help.
'love those Mullards!