Unfortunately it is true that drugs in our society are common enough that home buyers need to use caution in choosing a home. Drug production can cause havoc with home systems and leave lasting and often unseen danger behind.
There could be yellow or red stain marks on countertops, carpets, or linoleum. I may find iodine stain marks on walls, blocked out windows, burns in countertops, on rugs, or on the floors, discarded cylinders, empty solvent jars or mason jars, these are often tossed into bushes and shrubbery at back of property.
Plastic tubing is a common find, usually small discarded lengths, again often thrown about the property. You will often see rock salt or rock salt containers in a garage, but when you find 6-8 then it can be an indicator especially if you also find hydrogen peroxide bottles. Usually you will find large bulk size containers but sometimes you will find discarded cardboard cartons from cases of home size large bottles. Discarded lithium batteries, red stained coffee filters and unusual smells, such as a strong cat urine smell, ammonia, or vinegar odours are also all indicators of unusual home chemical use.
Indoor marijuana grow operations can be found in places such as houses, apartments, commercial businesses and abandoned factories. There are thousands of marijuana growers in the United States, but the problem is considerably more serious in Canada. In Canada, marijuana grow operations are becoming so common that many police departments have given up trying to fight them. 
Grow operations can be found in any type of house and community. Homes with grow operations are not necessarily cheap rentals or suspicious-looking, crumbling old homes in ramshackle communities. Newer homes in upscale communities are increasingly used to hide grow operations. There seems to be a swing towards these homes as they have larger electrical services, they are often in areas where most people work away from the neighborhood and this gives growers the privacy they want, and they have easy access to highway systems for moving goods. 
Heat and humidity are very destructive forces to a homes structure and its components. Water that is fed to plants will transpire and evaporate from the containers into the surrounding air. Cannabis plants also require warmth. Excess water vapour and high temperatures can lead to different defective conditions.
Grow operations, even relatively small ones, require an enormous amount of electricity for lighting. Some utility companies will report suspiciously high levels of consumption to police. In order to avoid this possibility, growers will often illegally bypass the electric meter to gain access to electricity without any record of the theft. They accomplish this by tapping electricity from the power lines before they reach the meter. I look for any type of inventive yet improper or dangerous electrical connections, and for evidence there was an improper hook up because after the electrical has been disconnected the only evidence a home inspection may reveal as a clue may be an extra set of mast clamps on the service drop pole.
Venting plays a huge part in making grow ops work so this aspect is sometimes the only evidence left after coverup repairs. During my home inspections I get very suspicious when I see chimneys that have been repaired in more than one area inside the home and when I see 2x2 patches of clean roof sheeting high up on the roof it usually means repairs have been made to areas that were roughly cut out for additional vents. I start looking very closely at drywall ceilings then to see if there are repairs in each room.
As a home inspector dedicated to client service I keep my eyes and my nose open.
