Kitchen Exhaust
& Makeup Air Balancer
Audit commercial extraction hood displacement metrics against makeup air fan injections to neutralize envelope pressure drops.
Commercial Kitchen Mass Ventilation Thermodynamics & Building Envelope Sizing Physics Overview
Commercial food-service facility ventilation operations represent some of the most intensive volumetric fluid challenges in the modern built environment. Heavy gas-fired cooking appliances (like broilers, ranges, and woks) generate massive thermal plumes loaded with aerosolized grease particles, water vapor, and high-temperature combustion bi-products. To capture this hazard profile, mechanical upblast exhaust fans pull immense quantities of air out of the building through stainless steel capture hoods. According to fundamental mass-balance conservation rules, any air quantity pulled out of an enclosed envelope must be concurrently replaced ($CFM_{\text{exhaust}} = CFM_{\text{supply}}$). If a facility fails to deploy a dedicated mechanical Makeup Air (MUA) fan system to return roughly **85% to 90%** of the exhausted volume, the property falls into a severe negative structural pressure state. This heavy vacuum draws unconditioned outdoor air through cracks, doors, and window assemblies, destroying the indoor climate control balance.
Frequently Asked Questions
A: Standard mechanical ventilation design rules dictate that the kitchen core must retain a slight negative air pressure boundary (approx. 10% lower than the adjacent spaces). This slight vacuum acts as an invisible aerodynamic barrier. It ensures that whenever doors swing open, fresh air drifts inward from the dining zone toward the line, pinning all hot air currents, cooking odors, and airborne grease molecules under the extraction hood canopy instead of allowing them to cross-contaminate customer seating areas.
A: Back-drafting occurs when a massive mechanical exhaust hood starves a kitchen of makeup air, causing the building to pull air from any available opening to satisfy its vacuum. If the property operates atmospheric gas-fired appliances nearby—such as natural draft hot water heaters or heating boilers—the building vacuum will overpower the natural upward thermal draft of the appliance exhaust flues. This turns the flue into an air intake line, pulling combustion exhaust gases containing toxic carbon monoxide straight back into the property.