Night Purge is a controlled ventilation process that exchanges indoor air with cooler outdoor air during nighttime hours to reduce indoor pollutant concentrations and prepare spaces for occupancy. This strategy improves indoor air quality and thermal conditions before occupant arrival in the morning.
Operational Characteristics
Night purge operates 2-4 hours before occupancy begins, typically between 5-8 AM, when outdoor air quality is generally superior to daytime conditions. The process exchanges 6-10 air changes per hour, requiring outdoor air dampers and exhaust capability. Systems must include carbon monoxide and ozone sensors to prevent drawing contaminated air during high-pollution periods.
Applications and Benefits
Night purge particularly benefits office buildings, schools, and retail spaces that experience elevated CO2 and volatile organic compound concentrations during closed-building hours. It improves thermal comfort by establishing cooler baseline temperatures and removing overnight pollutant accumulation. The process requires 15-30% of standard ventilation fan power.
Practical Implementation
Night purge requires building automation systems with scheduled controls and outdoor air quality monitoring. Implementation costs are minimal when integrated into existing ventilation systems, typically adding only damper controls and scheduling logic to existing HVAC infrastructure.