Jamaican Cess- "smoke" is a mixture of vaporized tars and cannabinoids, particulate carbon, CO2, CO, and H20. The Vaporized tars are not exactly solid (more of a viscous liquid)m but the CO2, CO, and H20 are all gas. In fact, when you burn anything, the reaction combines the Oxygen in the air with whatever's burning, meaning the smoke you're pulling in has almost no oxygen in it.

Some of the early studies damning marijuana (think 1930's) were reexamined, and scientists realized all the damage being done was from Carbon Monoxide poisoning and lack of oxygen--but that was only because they pumped pure smoke and no air into gas masks for 5 minutes straight, which has the same effects as leaving your car running in a closed garage for about 5 minutes--not good. While this is only a small risk when smoking, it must be considered that every breath of smoke is, effectively, one breath of everything except oxygen.

However, the "before bed" part is bullshit.