CAN I ASK A GUEST TO VAPE OUTDOORS?

The risks of secondhand smoke are well known, so declaring your home a no-smoke zone is socially acceptable.  These days, most smokers are accustomed to going outside to light up since most public venues are nonsmoking.  Vaping, on the other hand, can be more difficult to control, especially when people insist that vaping is smokeless,  so "it shouldn't be a problem."
According to the surgeon general, the chemical mix of aerosol, including nicotine, released by e-cigarettes have been found in secondhand aerosol.  If you don't want guests to vape in your home, gently remind them of the facts and ask them to step outdoors.