Combined optical solutions. There are actually numerous proprietary optical smoke measurement equipment like the 'nephelometer' or maybe the 'aethalometer' which use several different optical solutions, which include multiple wavelength of light, inside of an individual instrument and apply an algorithm to provide a great estimate of smoke. Evanston firefighters https://broadfar.com/non-combusted-cigarettes-a-safer-alternative-or-just-a-myth/