By Kent · Lock Depot Staff Writer

Von Duprin 3547A: A Fire-Rated Exit Device for a Stairwell Door

A stairwell discharge door on a rated corridor needs an exit device that's actually listed for that opening, and a panic bar that merely fits the prep won't cut it. Surface vertical rod devices like the 9927 work well on a lot of pairs, but the rods run exposed down the face of the door, and that look (and that hardware) isn't always what a rated stairwell wants. The Von Duprin 3547A Series is the concealed vertical rod answer: the rods hide inside the door stile, the device is UL listed for fire exit hardware, and it's built specifically for openings where the rating actually matters.

What "concealed" and "fire-rated" mean on this device

Unlike a surface-mounted rod, the 3547A's top and bottom rods run inside the door itself, so the face of the door reads clean, just the touch bar and the device body. That's a real advantage on a public stairwell or a corridor where a client doesn't want exposed hardware running the height of the door. On the fire side: this device is UL listed for fire exit hardware, and the listing comes with a real restriction worth knowing before you order. Fire-rated concealed vertical rod devices ship with no mechanical dogging. You cannot hold the latch retracted mechanically on a rated door, full stop, because code requires the door to self-latch every time it closes. If someone tells you to dog this device open for a busy period, they're asking for a code violation.

The device is also ANSI/BHMA A156.3 Grade 1 certified and non-handed: one part number fits either a left-hand-reverse or right-hand-reverse door, which simplifies the order if you're not 100% sure of the door swing when you're placing it. It ships in a 3-foot width and mounts on aluminum, glass, hollow metal, or wood doors.

Exit only, or add a night latch

Order the base 3547A-EO-F for an exit-only function: touch bar operation from the inside, no outside trim, no cylinder required, and free egress at all times from the inside. That's the right call for a true stairwell discharge door where nobody needs to come back in through this leaf. If the door also functions as a controlled entry point after hours, the 3547A-NL night latch configuration adds an outside lever that locks and unlocks by key, while the inside stays free for egress at all times regardless of the outside lock status. The night latch version ships less cylinder, meaning you order a mortise cylinder separately to match the building's existing keyway rather than getting stuck with a cylinder that doesn't take your master key system.

Both configurations carry a 10-year mechanical warranty, the longest term in the Von Duprin line, which tells you something about how the company rates the device's own service life on a door that gets used every single day.

Field-check before the device ships

Positive latching at both the header and the threshold is the entire point of a concealed vertical rod device on a fire door, and it only works if the door itself is square and the hinges are in good shape. If the door is sagging even slightly, the top rod won't reach the header strike with enough engagement to latch fully, and you'll have a fire door that looks closed and locked but isn't actually latched where the code requires it. Fix the hinges and confirm the door hangs true before the new hardware goes in. Installing a brand-new listed exit device on a door that's out of square doesn't fix the door; it just hides the problem until the next fire inspection finds it.

If your opening is a narrow-stile aluminum storefront door instead of a wide stairwell leaf, the 9927 surface vertical rod or the 33A Series are usually the better fit. The 3547A's concealed-rod design needs stile width the narrowest storefront profiles don't always have.

Matching the rest of the opening

The 3547A shares its trim accessories with the rest of the 33A/35A family, so if you're already running Von Duprin hardware elsewhere in the building, this device drops in without forcing a second parts list. For the narrow-stile storefront cousin of this device, see the 33A Series; for the top-of-line pushpad on a hollow-metal fire door, the 98/99 Series covers that opening instead. Knowing which member of the family fits your door before you order saves a return shipment and a second round of paperwork with the AHJ.

Lock Depot is an authorized Von Duprin distributor, and every unit ships brand new in original manufacturer packaging with the full factory warranty behind it. Order before 2PM Eastern and most configurations ship the same business day, which matters when a fire inspector has already flagged a non-compliant device and the building has a re-inspection date on the calendar.

Common questions

Can I mechanically dog this device open during business hours?

No. Fire-rated concealed vertical rod devices, including the 3547A, ship with no mechanical dogging by code. The door must self-latch every time it closes. If you need a hold-open function, that has to be an electrified hold-open tied to the building's fire alarm, not a mechanical dog.

Does this device come with a cylinder?

The exit-only (EO) function needs no cylinder at all, since there's no outside trim. The night latch (NL) function ships less cylinder; order a mortise cylinder separately in your building's keyway.

Is it handed? Do I need to specify left or right?

No. The 3547A is non-handed and field-reversible, so one part number fits either swing. You will still specify RHR or LHR on the night latch configuration for the outside lever orientation, so confirm the door swing before ordering that version.

Why does the door need to be square before I install this?

The top and bottom rods have to reach the header and threshold strikes with full engagement to latch. A sagging door won't let the rod travel far enough, and the door can look closed without actually being latched, which defeats the entire purpose of the fire rating.

What width does this device fit?

The listed configuration ships for a 3-foot (36") door. If your opening is a different width, tell us before you order so we confirm the correct part number for your door size.

Browse the rest of the fire-rated and standard exit device lineup on the Von Duprin hub.