The Function Number Is the Decision, Not the Lever Style
When a commercial door schedule lands on your desk and you see a cylindrical latchset specified as a communicating or exit function, it is easy to gloss over the distinction and focus on the lever and finish. That is where projects go sideways. This article explains what each function actually does at the door, where each belongs on a door schedule, and what fire-rated openings require -- information useful to contractors pricing a job, facility managers reviewing maintenance replacements, and architects building out a hardware schedule from scratch.
What Is a Communicating Function Latchset?
A communicating function latchset (commonly called Function 125 or its ANSI equivalent F75 range) allows both sides of the door to retract the latchbolt freely -- no key required, no locked side. Either lever operates the latch from either face. This makes it a true free-passage device from both directions, but unlike a passage latch, it is categorized as communicating because the door typically connects two occupied spaces where both parties need unrestricted movement: think shared conference rooms, connecting hotel suites, interior clinic corridors, or pass-through storage rooms between departments.
The distinction from a straight passage latch is largely functional intent and sometimes hardware body -- but the operational result is the same: both sides always free. Where the spec matters is in the lock body and trim grade, which determines durability and fire-rating eligibility.
What Is an Exit Function Latchset?
An exit function latchset (Function 124 or ANSI F89) is free egress from the inside and secured -- or key-controlled -- on the outside. The inside lever always retracts the latch. The outside trim may be a fixed pull, a dummy lever, or a keyed lever depending on the trim package specified. This function is purpose-built for doors where people must always be able to leave freely but where re-entry from outside is controlled or denied without a key.
Common applications include:
- Stairwell re-entry doors in schools and office buildings
- Back-of-house doors at retail and restaurant facilities
- Mechanical room entries where staff exit but should not re-enter without authorization
- Side exits at healthcare facilities where patient egress must be unimpeded
Why the Confusion Happens on the Job Site
Both functions use the same cylindrical latchset body format, accept the same lever styles and finishes, and often look identical in the box. The difference lives in the internal cam and trim configuration -- and that difference only becomes obvious when the wrong one is installed and someone cannot get back in, or worse, cannot get out.
The most common field mistake is substituting a communicating function for an exit function on a stairwell door because both levers work seems safer. It is not -- it eliminates the access control the door was specced to provide. The reverse error, putting an exit function on a connecting corridor, means one side of the door now requires a key the occupant may not have.
Fire-Rated Openings: What Changes
If the door carries a fire label, the latchset must be fire-rated and UL-listed for use on that assembly. Several rules apply regardless of function:
- Positive latching is required. The latch must engage the strike positively when the door closes. Spring-latch designs on fire doors must not be held retracted (no dogging).
- The hardware must be listed for the fire rating of the door. A 20-minute label, a 45-minute label, and a 90-minute label each have their own listing requirements. Verify the latchset carries the correct UL listing for the opening.
- Both communicating and exit function latchsets can be fire-rated, but you must confirm the specific product carries that listing -- not just the body style. A Grade 2 product with a fire-rated UL listing, like the PDQ GP Series, is a practical option where the opening does not demand Grade 1 cycle counts but does require compliance.
- Dogging -- holding the latch retracted -- is never permitted on a fire-rated door. This applies to any cylindrical latchset function on a labeled opening.
Grade 1 vs Grade 2 on These Functions
Grade 2 cylindrical latchsets carrying a fire-rated UL listing are appropriate for many interior openings -- connected offices, light-traffic corridors, storage rooms. Grade 1 is warranted when cycle counts are high: main corridor connectors in schools, healthcare pass-through doors used by staff dozens of times per shift, or any opening the facility manager expects to service rarely. The PDQ GP Series sits in a useful middle position -- Grade 2 by ANSI rating but with a heavier-duty internal spec than most Grade 2 competitors, making it a value-conscious choice on moderate-traffic fire-rated openings.
For higher-demand environments, Corbin Russwin, Hager, and Sargent cylindrical lines offer Grade 1 communicating and exit functions with broader finish availability and longer warranty coverage.
Finish and Trim Selection
Both functions are available in the standard commercial finish palette. Satin chrome (US26D) is the most common specification on interior commercial doors for its durability and neutral appearance. On exit function latchsets, the outside trim choice drives the access story: a fixed pull gives exit-only behavior; a keyed lever allows controlled re-entry. Confirm with the architect or facility manager which outside trim is intended -- this is frequently left ambiguous in schedules.
Practical Checklist Before You Order
- Is the door fire-rated? Confirm the latchset carries the matching UL listing.
- Which function is required: free passage both ways (communicating) or controlled re-entry (exit)?
- What outside trim is specified for the exit function -- pull, dummy, or keyed lever?
- What is the expected cycle count and traffic level? Grade 1 or Grade 2?
- What finish is required, and does it match the balance of the opening hardware?
- Has the door prep been verified for the latchset body and backset before ordering?
Sourcing These Functions at DoorwaysPlus
DoorwaysPlus carries communicating and exit function cylindrical latchsets across multiple grades and finishes, including fire-rated options from preferred lines such as PDQ, Corbin Russwin, Hager, and Sargent. Whether you are replacing a single worn-out latchset on a healthcare corridor or specifying a full door schedule for a school renovation, the function number is the starting point -- and getting it right before the order ships saves everyone a return trip.
Browse cylindrical latchsets and fire-rated hardware options at DoorwaysPlus.com or contact the team for application guidance on your specific opening.