Temperature… Humidity & CO2 . What do they have in common? They are all environmental conditions inside a growing area that need to be controlled for successful gardening. The EVC-1 Environmental Controller controls all that and more. If you want a simple-to-use and reliable controller without spending hundreds of $, check out the EVC-. The EVC-1 provides extreme flexibility in a reliable solid-state environmental controller. Selectable CO2 , Temperature and Humidity modes allow the user to control temperature & humidity separately or together. Built in photocell activates CO2 device during the day. Night device outlet can control an exhaust fan / sulfur burner etc.