A new miniaturized kit based on very young supersensitive tobacco Bel-W3 plantlets, which can be easily used to detect phytotoxic levels of ozone in ambient air in large scale surveys, is described. It has been developed in laboratory as well as field studies. The optimal sampling time is 5-7 d. The advantages of the kit are its user-friendliness, low cost, and reliability. The kit may be integrated by a passive sampling tube set and may be also proposed for educational programs.