06/05/2026
The peep doors are the only way to see inside a live fired heater.
And yet they are frequently one of the last things considered in a heater project.
Get it wrong, and you get:
- Glass that cracks under radiant heat
- Doors that leak air and affect combustion efficiency
- Coverage gaps that leave sections of the firebox unmonitored
FIS peep doors are 100% sealed, rated for high-temperature heater service, and available in three standard types — glass, top hinged, and side hinged, all customizable to your application.
Glass Peep Door — 5" x 9" (customizable)
Glass rated to 1,800F. UV/IR scanning compatible. Air purging connections cool the glass during operation. For applications where operators need direct visual access through a sealed pane.
Top Hinged Peep Door — 5" x 9" (customizable)
Spring handle operation. Tightly sealed against air infiltration. Cost-effective option for standard inspection access.
Side Hinged Peep Door — 8" x 16" (customizable)
3x the viewing area of a standard door. Covers burners, shock tubes, refractories, and tube supports from a single position. Tight locking mechanism for reliable sealing.
Replacing an existing door or specifying a new heater?
We can turn around specs and lead times fast.
Drop your inquiries here- https://www.heatflux.com/peep-door-inquiry-form