Hydrogen in it's natural form does not.
But Traveller ships use liquefied hydrogen for fuel... hydrogen that's been concentrated and super-cooled to a liquid state. This concentrates all the impurities picked up in the random gas giant you scooped the fuel from, which are then mostly removed in the purification process. Liquid hydrogen is super-cooled to maintain its liquid form and is highly dangerous to unprotected people, especially in the closed environment of a starship. You really don't want that crap in your L/S system.
Therefore it's reasonable to presume that a negative and unique smell is introduced into the gas that automatically the crew that the L-Hyd is leaking somewhere. That's a common safety procedure in gas companies today.