Atmospheric Controller (SPECIAL ORDER) Solatel Atmospheric Controller (SOLTHP-100) (SPECIAL ORDER) The Solatel THP-100 coordinates ventilation and CO2 (carbon dioxide). This is required when temperature and humidity are controlled by a vent or exhaust fan. Hot or humid air is blown out of the growing area and fresh air is then drawn in. This continues until both temperature and humidity fall below the dial settings. CO2... — Ships from HF: OR, CA, CO, PA, TX, FL USA....more info.