Article 2-4 The Odor Problem

Often an arrival to a hydroponic grow room is preceded by its odor.

A lot of research, effort and attention has been devoted to the stale, damp odors that can emanate from hydroponic gardening.

Ionization, chemical deodorizers and ozone systems have all been touted to treat the situation, but before discussing the correct solution, let’s first analyze the problem. Typically, a hobbyist has a grow room set up in an area of the home which is not environmentally isolated. Therefore, the entering and exiting of the hydroponic grow room allows odors to spread throughout the home. Additionally, the lighting in the hydroponic grow room creates an enormous amount of heat which, along with the stale odors, is exhausted to the outdoors. The ideal solution would provide a home with air that is naturally fresh and clean smelling with neutral hydroponic system exhaust. Essentially, no detectable odors in or outside the home. When correctly employed, ozone air treatment is the one solution that meets these critical demands.

We have all experienced the exhilarating effects and the clean fresh fragrance of the air after a thunder storm. The spice of this fragrance is ozone. Ozone (03), a triatomic (3 atoms) form of oxygen, is a normal trace element in the earth’s atmosphere. It is created by the action of short-wave length ultraviolet light from the sun on the oxygen in the air (the ozone layer in our stratosphere). It is also created in nature by lightning and man-made through electrical discharges (sophisticated automotive “spark plugs”) such as arc welding.

Chemical deodorizers merely mask odors and ionizers only charge air particles so that they fall to the earth. Beyond providing its own fresh air aroma, ozone actually binds with the odor molecules to neutralize odors at the source. Natural low levels of O3 are in the air we breath at all times. The maximum level of O3 in the air that all government regulatory agencies consider 100% safe for people, plants and pets is 0.05 ppm. O3 levels are accurately tested with an “Eco Badge,” an inexpensive test kit used to establish an initial ozone level at which odor is effectively eliminated without any side effects (light headedness, headaches, dry throat and in the extreme, nausea) that may be caused from high concentrations.


To prevent the escape of odor to the other areas of the home, only ultra-violet (UV) ozone lamp generators should be used. A 0.05 ppm level inside the grow room is recommended. UV ozonators (14″ bulb length or less in length) produce appropriate levels of O3. Another benefit to low levels of ozone in the grow room is the small amounts of CO2 being created by the ozone’s oxidization of the organic debris in the air.


When outside ventilation is used, an adjustable corona discharge system is the answer. An exhaust system requires a more sophisticated, variable output O3 system. The level of odor intensifies as plants grow to maturity, therefore, it is necessary to increase the O3 output gradually. Heat is the enemy of O3 and therefore the O3 output must be increased as the heat increases. UV ozonators are not adjustable and so only electronic corona discharge systems will provide the adjustable high levels of O3 required. As the heat and odors increase, the electronic ozonator is adjusted with the turn of a knob to the increasing amount of O3 required to provide a fresh air scent at the exhaust outlet.

A well managed and properly equipped ozone air care program will control odors and increase the success and overall enjoyment of hydroponic gardening.