How far apart should grease duct access panels be?

The working rule on horizontal runs is an opening at each change of direction and no more than 12 feet between openings along a straight run. The exact requirements are in NFPA 96 Chapter 7, and the authority having jurisdiction decides what is acceptable on a given job.

Does this tool approve a duct layout?

No. It draws a planning sketch for a walk-down or a quote. Opening locations are set by the duct installer and the authority having jurisdiction.

See where the duct access openings would go.

Enter the horizontal runs and any riser. A sketch shows an opening at each bend and no gap over 12 ft.

Describe the duct

Enter each straight horizontal run from the hood outward. A bend sits between each run.

Job (optional)

Horizontal runs, in feet

From the hood

After bend 1

Floors the vertical riser passes (0 if none)

Opening plan

Openings on the run: 4
Longest gap: 10 ft
On the riser: 1

Opening for spacing Opening at a bendStraightened out, to scale along the run.

9 ft from the hood, run 1
18 ft from the hood, run 1, at the bend
28 ft from the hood, run 2
38 ft from the hood, run 2

How the sketch is worked out

An opening at each change of direction, then more along each straight run so no two openings are more than 12 ft apart. The hood and the far end count as reachable. A vertical riser gets one opening per floor it passes. Where a person has to enter the duct, NFPA 96 calls for openings of at least 20 in by 20 in.

This is a planning sketch for a walk-down or a quote, not an approval. Where openings go is set by the duct installer and the authority having jurisdiction under NFPA 96 Chapter 7.

Keep this result

Email a copy or turn it into a report.

Your result stays available here. Email delivery is requested by you; product tips are optional.

Why openings decide the job.

A duct you cannot reach is a duct you cannot clean. Missing or painted-over access panels are among the most common reasons a run is left uncleaned and written up as not accessed on the report.

Walk the run before quoting: count bends and measure the straight lengths.
Note where the plan calls for an opening and none exists. That is a finding for the customer.
Photograph each opening you use, open and closed, for the service record.
List any section you could not reach as not accessed, with the reason.

A sketch, not an approval

This planner applies two spacing rules to the lengths you enter. It does not replace NFPA 96, the mechanical code, the duct installer's drawings, or the authority having jurisdiction, who decide where openings go.