Some nic bases have an odd chemical smell. I bought some in 2013 that had a rather pungent smell. Like kerosene or rubber. I sent it back and the replacement bottle had a similar but much fainter smell.
I've tried all the big name suppliers. Even in a flavored mix I can still smell the nic base and identify which brand it is most of the time.
I doubt this is the case with the OP but it's at least in the realm of possibility. Are the juices you are smelling gas in from the same vendor? Even if not, many vendors use the same suppliers.
You can smell nic base in any mix. Just smell the drip tip after a vape. It's always there and ranges from slightly ashy, to a tobacco note, a woody note, to a chemical note, to a petroleum note. Even "musty" but pleasant is in the realm of normal nic base smell. It's rarely strong enough to be unpleasant no matter who the supplier is though.
I vape unflavored about 50% of the time and have grown quite fond of several nic bases. They have a unique flavor all on their own. Unflavored doesn't = no flavor.