Zephyr · Buying Help
How Much CFM Do I Need Over My Grill?
The industry rule is 100 CFM per 10,000 grill BTU, with the hood 30-36" above the cooking surface. Zephyr's outdoor hoods peak at 1200 CFM — that covers a single 36-42" built-in gas grill with margin.
By Reed · Updated November 10, 2026
What you need
CFM sizing by grill BTU
- Small grill (30-36", 40-60k BTU)
- 400-600 CFM (any outdoor hood is fine)
- Mid grill (36-42", 60-90k BTU)
- 600-900 CFM (Zephyr Cypress/Spruce handles this)
- Large grill (42-48", 90-120k BTU)
- 900-1200 CFM (Zephyr outdoor is at the upper end)
- XL grill (48-56", 120-150k BTU)
- 1200-1500 CFM (consider dual Cypress or indoor-rated larger hood under cover)
- Side burner only
- +200 CFM to the base calc
- Charcoal / wood-smoker cook
- +30% to the base calc for smoke load
Step by step
Find your grill's total BTU rating
Look up the grill's primary burner BTU rating in the spec sheet. Add the sear burner if it has one. If the grill has a rotisserie or side infrared, include those too.
Apply the 100-CFM-per-10k-BTU rule
Divide total BTU by 100. A 90,000 BTU grill wants 900 CFM minimum. Round up to the next hood size available.
Add margin for smoke-heavy use
If you plan to use lump charcoal, wood chunks, or heavy smoking regularly, add 25-30% to the baseline CFM.
Confirm hood hang height in the install plan
Hood at 30-36" above the cooking surface. Higher = smoke spreads before capture; lower = hood catches heat and slower cooks.
Common mistakes
- Sizing the hood off the grill width alone. A 36" grill and a 36" hood look balanced but the hood misses side smoke. Match width to grill-plus-6-inches-each-side.
- Picking max CFM and ignoring duct size. A 1200 CFM blower pushed through 6" duct delivers maybe 500 CFM of actual air movement. Match the duct to the hood spec.
Hands-on tips
- If you can place the grill on a wind-exposed side of the patio, natural ventilation does half the hood's job. Pair wind + hood for the best smoke capture.
- Grill under an enclosed patio with 3 walls? Upsize the hood by one tier — enclosed spaces trap smoke against the ceiling.
Questions people ask
My grill is 90,000 BTU — is 1200 CFM overkill?
No. 900 CFM is the floor; 1200 CFM gives margin for sear sessions, flare-ups, and smoke-heavy cooks. The hood won't over-exhaust at a lower setting — most hoods have 3-4 speeds.
What about a makeup-air requirement?
Indoor hoods above a certain CFM (varies by state) trigger makeup-air code. Outdoor hoods do NOT — the outdoor space is the makeup air. Confirm with your local code if your patio is partially enclosed.
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