Ambient Temperature and Relative Humidity Remained Stable after Prolonged Application of Superheated Steam in Enclosed Spaces

Superheated steam has been proposed as a novel tool for surface sanitation, yet its impact on the relative humidity (RH) and temperature within enclosed dry food processing environments for extended exposure is unknown. This study measured RH and temperature within 12 enclosed and semi-enclosed indoor spaces of varied size, air handling systems, and ventilation rates during prolonged (<5 h) superheated steam operation at 135°C. The RH and temperature were monitored at locations near (0.3 and 1.5 m) the steam nozzle, entrances, vents, and walls. Superheated steam application did not significantly (P > 0.05) increase the ambient temperature or RH among all spaces, except near the steam source (0.3 m). A significant increase in RH and temperature occurred near the steam source (0.3 m), where the maximum increase in RH (47%; small facilities, high ventilation rate) and temperature (9.3°C; large facilities, low ventilation rate) was observed, resulting in limited steam cooling and surface condensation. The results suggested that prolonged superheated steam exposure did not substantially increase the RH or temperature, except for small facilities with low ventilation rates and locations near the steam source. This indicates that the application of superheated steam could enhance sanitation efforts in dry processing environments.