AirClear Kitchen

Guide

Do I need makeup air?

Powerful exhaust removes air from the kitchen; replacement air must enter from somewhere. In tightly sealed homes, aggressive exhaust can depressurize the house enough to pull air down unintended paths—including chimneys and wall gaps. Whether you need dedicated makeup air depends on flow rate, envelope tightness, and local code.

The household as a leaky balloon

Houses are not sealed chambers; they are assemblies of intentional openings (windows, dampers, vents) and unintentional leaks (electrical penetrations, top plates, garage doors). When a kitchen hood exhausts at high CFM, the pressure indoors can drop slightly relative to outdoors. The larger the exhaust rate relative to easy infiltration, the more pronounced the effect.

That pressure difference matters because it changes the direction of airflow across every hole in the envelope. A mild draft under a door can become a strong draft; a chimney flue can reverse flow under the wrong conditions. This is not “theoretical”—it is a routine reason why builders ask about makeup air when specifying ducted hoods with high flow rates.

What “makeup air” usually means

Makeup air is a controlled path for outdoor air to replace what the exhaust fan removes. It may be passive (dampers, grilles) or actively managed; it may be tempered or untempered depending on climate and code. The goal is to avoid extreme depressurization while still clearing cooking pollutants.

Implementation is not a DIY guess—duct routing, freeze protection, and interaction with heating systems are site-specific. This article is not a substitute for a qualified professional who understands your local code and your mechanical systems.

Interaction with combustion appliances

If a home relies on naturally drafting appliances or has open-combustion devices, depressurization can raise safety concerns. Modern codes often address these interactions explicitly. Even if your kitchen exhaust is modest, cumulative exhaust from dryers, bath fans, and hoods can matter.

Smoke behavior and capture

Depressurization can also interact with smoke movement in surprising ways: sometimes plumes are pulled toward leaks instead of toward the hood inlet. That is why pressure balance belongs in the same conversation as capture geometry and hood dimensions.

What to ask a professional

  • At what exhaust rate does your jurisdiction require makeup air?
  • How tight is this home, and how does the hood interact with other exhaust devices?
  • If makeup air is added, where will it enter and how will it be conditioned?

If your hood is not ducted outdoors, the pressure story differs—see recirculating hoods—but grease and filter maintenance remain non-negotiable; see filters and fire sense.