Smoke grenades fill a place with obscuring white smoke. How does this affect a vampire using Auspex 1? Can they see through the smoke, or otherwise know what's happening (by hearing footsteps, etc.)?
Auspex I is Heightened Senses, i.e. increasing one of your five senses to supernatural levels (NOT aura perception). I personally always make my players define what sense they enhance.
So if it is anything other than Sight or Smell - use as normal. Hearing footsteps is perfectly fine. Smell would be overloaded, possibly leading to WP roll to avoid Frenzy, and Sight would be enhanced, but the smoke is still there. I'd say a kindred with heightened sight would be better off, but not as good as in pitch dark. They'll see silhouettes better, but they'll also see a lot of smoke, and it will distract them.