Smoke Alarm Distances From Cooking Appliances and Bathrooms

Why this matters

A kitchen remodel that moves the range 6 ft toward the hallway can put a code-compliant smoke alarm out of compliance without anyone touching it. A bathroom addition that puts a shower door at the end of the bedroom hall can do the same. The alarm then goes off with every steak and every hot shower, and within a few weeks someone in the house has pulled it down. The fix is a few feet of measurement before the ceiling is closed. This card is the distance rule itself and how to measure it; the choice between sensing types is on its own card (see related: Smoke Alarm Sensing Types and Which Belongs Where in a House).

The rule, as the 2021 IRC writes it

In the 2021 IRC, as adopted by your jurisdiction, the near-cooking clearances are a subsection of R314.3 (R314.3.1 in that edition; confirm the number in the edition on your permit, because these sections have moved between cycles). Paraphrased:

• An ionization smoke alarm is not installed less than 20 ft horizontally from a permanently installed cooking appliance.
• An ionization smoke alarm with an alarm-silencing switch is not installed less than 10 ft horizontally from one.
• A photoelectric smoke alarm is not installed less than 6 ft horizontally from one.

The bathroom rule sits in R314.3 itself: a smoke alarm is installed not less than 3 ft horizontally from the door or opening of a bathroom that contains a bathtub or shower.

Every one of these carries the same condition, and it is the half that gets dropped: each clearance applies unless keeping it would prevent placing a smoke alarm in a location R314.3 requires. The code would rather have an alarm too close to the range than no alarm outside the bedrooms. That exception is narrow. It applies only when no spot that meets the distance also meets the required-location rule, not when the compliant spot is inconvenient to wire.

Some states and cities amend R314 or have their own alarm rules that are stricter near kitchens and baths, and a few required photoelectric units in these zones before the IRC did. Read the adopted text.

What "permanently installed cooking appliance" covers

The clearance runs from a permanently installed cooking appliance: a range, a cooktop, a wall oven, a built-in grill. A countertop toaster oven or an air fryer on the counter is not one, so the code distance does not run from it. The nuisance does, though, and a smart placement treats the counter where the toaster lives as part of the kitchen.

How to measure it

The IRC says "horizontally." Measure on plan, at ceiling level, from the nearest edge of the appliance to the alarm. Two cautions.

Straight line versus path. NFPA 72 measures its near-cooking zones along the path smoke would travel, which around a wall or through a doorway is longer than the straight line. A straight-line measurement is the shorter of the two, so if the straight line clears the distance, the path does too. Use the straight line as your check and you are on the safe side of both documents.

Measure the appliance, not the cabinet run. The distance starts at the cooking appliance, not at the end of the countertop. On a remodel, measure from where the range will actually sit, from the drawings or from the rough-in, not from where the old one was.

The diagram: one hallway from range to bath

A range at the kitchen end of a bedroom hall, a bath with a tub at the far end. Distances along the hall from the nearest edge of the range.

KITCHEN                                     BATH
[RANGE]                                    (tub)
  |                                          |
  0 ft    6 ft     10 ft            20 ft    door
  |-------|--------|----------------|--------|
  |  no   | photo  | photo, or      | any    |
  | alarm | only   | ion with       | type   |
  |       |        | silencer       |        |
                                   |<-3 ft->|
                                   no alarm here
                                   (bath door)

The bands do not overlap kindly in a short hall. In this drawing the plain-ionization band starts at 20 ft and the bath-door exclusion starts at 3 ft before the door. If the bath door sits at 22 ft, the only spot for plain ionization is between 20 and 19, which does not exist. That is the arithmetic behind why most halls end up photoelectric.

NFPA 72's version, without the figures

The IRC points to NFPA 72 for installation, and NFPA 72, in the edition your jurisdiction adopts, has its own near-cooking provisions. It defines an exclusion zone around a fixed cooking appliance inside which alarms are not installed, and a band beyond it in which an alarm has to meet a stricter condition: in recent editions, a listing for resistance to common cooking nuisance sources. Its figures and wording have changed between editions, so this card does not restate them; read the edition your building department enforces. Where the IRC and NFPA 72 differ, the AHJ decides which governs, and following the stricter one satisfies both.

NFPA 72 also keeps alarms clear of forced-air supply registers and the tips of ceiling fan blades, because the air from either can blow smoke away from the chamber. That matters to an HVAC crew moving a register on a hallway ceiling, and the alarm maker's instructions usually repeat the clearance.

Worked example: a hall that only fits one answer

A remodel moves a range to the end of an open kitchen. The bedroom hall starts at the kitchen opening and runs straight to a bathroom with a shower. The required alarm outside the sleeping area has to go in this hall, in the immediate vicinity of the two bedroom doors.

The measurements, from the nearest edge of the new range:

• Range to the kitchen opening: 4 ft.
• Hall length: 16 ft, so the bath door is at 4 + 16 = 20 ft from the range.
• Bedroom doors at 10 ft and 15 ft from the range.

Apply each clearance.

• Bath door at 20 ft, 3 ft clearance: the alarm must be at 20 - 3 = 17 ft or less.
• Photoelectric, 6 ft: the alarm must be at 6 ft or more. Window: 6 to 17 ft. The hall itself starts at 4 ft, so the usable window is 6 to 17 ft. Open.
• Ionization with silencer, 10 ft: window 10 to 17 ft. Open.
• Plain ionization, 20 ft: needs 20 ft or more, but the bath clearance stops at 17 ft. No window. Out.

Choose the spot. The bedroom doors are at 10 and 15 ft. A point between them, around 12 to 13 ft, is in the immediate vicinity of both and inside both open windows. The existing alarm is an old ionization unit at 8 ft. At 8 ft it fails the 10 ft silenced-ionization limit, so even if it had a silencer it could not stay there. Two choices: relocate the base to about 12 ft and install a photoelectric unit, or leave the base at 8 ft and install a photoelectric unit there (8 clears 6). The crew relocates, because 12 ft also serves both bedroom doors better, and the ceiling is open anyway.

Recheck from the other end. From the bath door, 12.5 ft from the range is 20 - 12.5 = 7.5 ft away, comfortably past 3 ft. From the range, 12.5 ft is past 6 ft and past 10 ft. Both ends close.

What changes the answer.

• The hall is shorter. Say the bath door is at 9 ft from the range. Photoelectric needs at least 6 ft, the bath clearance caps it at 9 - 3 = 6 ft. One point, exactly at 6 ft, is the only compliant spot. If the bedroom doors are not near it, this is the case the exception exists for: the required location wins and the alarm goes where the bedrooms need it, with a photoelectric unit carrying the cooking-nuisance listing. Document the measurements and ask the inspector before rough-in, not at final.
• The hall turns a corner. A range 8 ft from the alarm in a straight line through a wall may be 13 ft around it. The IRC check uses the 8 ft. Under NFPA 72's path measure the answer may differ; follow the AHJ.
• There is a ceiling fan or a supply register. Move the alarm off the fan blade tips and the register's throw even if the cooking distances are met.

Write the measurement down where the next crew will find it

An inspector, or a crew on a later job, will ask why the alarm is where it is. A one-line note on the job answers it: the appliance measured from and which edge, the straight-line distance to the alarm, the alarm's sensing type and whether it has a silencer, and the distance to the nearest tub or shower bath door. For the hall above that reads: "New range, nearest edge to hall alarm 12.5 ft straight line; photoelectric, no silencer; shower bath door 7.5 ft." If the exception was used, the note says which required location forced it and that the inspector was asked. An island cooktop is the case that most needs the note, because it can sit within a few feet of three different ceiling spots and every one of them has to be measured.

Failure modes that a tape measure catches

Measuring from the old range. The alarm was compliant to the old layout. After the remodel nobody measures again, and the new range is 7 ft closer. The fix is to make "re-measure alarm distances" a line on the close-in checklist for any job that moves a cooking appliance or a bathroom door.

Forgetting the bath is a bath now. A powder room that becomes a full bath with a shower has just created a 3 ft clearance around its door. The alarm that was 2 ft from a powder room door is now out.

Using the exception as a shortcut. "It would be hard to get wire there" is not the exception. The exception is that no compliant location exists for a required alarm. If one exists, it is used.

References

• International Residential Code, 2021 edition as adopted by your jurisdiction: R314.3 and its near-cooking subsection (R314.3.1 in that edition)
• NFPA 72, National Fire Alarm and Signaling Code, in the edition your jurisdiction adopts: single- and multiple-station alarm installation, including near-cooking zones and register and ceiling fan clearances
• Alarm manufacturer installation instructions, which bind through the listing
• See related: Smoke Alarm Sensing Types and Which Belongs Where in a House; Smoke Detector Placement + Types Reference; Smoke and CO Alarm Requirements Your Permit Triggers