A system that provides effective and efficient introduction of water droplets into an air flow. The water droplets are sufficiently small so as to evaporate primarily before leaving the mixing enclosure where the droplets are injected by spray nozzles. Large droplets are kept to a minimum, thus reducing condensation and water accumulation to a very small amount. An amount of water usage is significantly less than that of a conventional evaporative humidifier of the same capacity. The present system may be placed in an enclosure that can readily replace other conventional evaporative humidifiers in enclosures. The present enclosure and system may be installed in lieu of a conventional enclosure and evaporative humidifier with minimal effort. The present enclosure has features that facilitate droplet to air mixing, viewing, humidification, and testing. In permissible situations, the present system may replace a conventional system but retain the conventional enclosure.