Vaping, smoking, and cannabis

Cigarettes, cigars, cannabis, and e-cigarettes all add particles to indoor air, but they are not interchangeable. Tobacco combustion produces a broad particle distribution carrying thousands of identified chemicals, dozens of them carcinogenic; the Surgeon General's reports on smoking and health remain the authoritative summary of secondhand exposure.

Cannabis smoke is chemically similar to tobacco smoke at the combustion level: fine and ultrafine particles, polycyclic aromatic hydrocarbons, benzene, formaldehyde, and other partial-combustion products, with cannabis-specific compounds (THC, CBD, terpenes) added rather than substituted, as CDC notes. The method matters. A joint or pipe produces a smoke-level particle spike; a bong lowers particles only slightly; vaporized concentrates cut particles sharply but can raise VOCs from terpenes and residual solvents; a blunt combines tobacco and cannabis smoke.

E-cigarette aerosol is different: no combustion, but heating the liquid produces an aerosol of propylene glycol, glycerin, nicotine, flavorings, and trace metals, and its health effects are still under active investigation; CDC maintains current guidance. Much of the aerosol is in very small droplets. The SEN66 sizes particles from 0.3 µm up, so it cannot see the smallest ones, but the larger part of the cloud shows clearly as a PM₁ and PM_2.5 spike that usually clears faster than smoke.

On the sensor, any of these reads as a sharp PM_2.5 spike (50–300+ µg/m³ during a session, depending on room size and ventilation) with a VOC-index rise. Smoke's VOC tail can outlast the particles by hours: after a long session, PM may clear within an hour or so while the VOC index stays up for much longer. Thirdhand residue, the particles and chemicals deposited on surfaces, keeps releasing trace VOCs after smoking ends; it is the source of the "smoker's home" smell.

In apartments and condos, smoke and odor travel: through shared ventilation, gaps under doors, and bathroom-fan ducts. Smoke drifting in from a neighbor's unit is a common complaint in multi-unit buildings, and it shows on the sensor as a particle and VOC rise with no source in your own home. See apartment and condo IAQ.

If household members smoke or vape: keep it outdoors. If that isn't possible, open a window and run an exhaust fan in the same room during and after the session, avoid bedrooms and any room a child or someone with asthma uses regularly, run HEPA filtration in adjacent rooms, and keep a MERV-13 HVAC filter to clear residual particles. Don't use ozone generators or "odor eliminator" sprays as a substitute: ozone is itself a respiratory irritant. See reducing VOCs indoors.