Can you absorb THC through your skin if you walk into a room filled with marijuana smoke?

Yes, small amounts, but not enough to be noticeable. You would have to be in an extremely smokey room for hours to barely feel it, but you would probably feel it from breathing it in first, after about 15 min of heavy secondhand smoke. It would leave your body fast, within the day, you could eat pot everyday and completely fine. If you hold a sticky bud in your hand for 20 minutes in the sun, you will sweat and feel the stickiness and effects of the herb.