What Is a Removable Mullion and How Does It Work?

When selecting hardware for a pair of commercial doors, it is important to consider how the doors will operate and how the opening will be used.

Some double-door openings require both doors to operate independently while still allowing the full width of the opening to be available when needed. One hardware option that can provide this flexibility is a removable mullion.

Removable mullions are commonly used in schools, hospitals, warehouses, and other commercial buildings where both secure latching and occasional full-width access are important.

What Is a Removable Mullion?

A removable mullion is a vertical metal post installed between a pair of doors that can be removed to create a wider, unobstructed opening.

Unlike a fixed mullion, which stays in place, a removable mullion is designed to be detached when the full width of the doorway is needed.

When installed, the mullion provides a center latching point for rim exit devices, allowing each door to latch independently.

How Does a Removable Mullion Work?

A removable mullion is installed vertically between two doors, typically extending from the floor to the top of the door frame.

The mullion is secured using mounting hardware at the top and bottom of the opening.

When the mullion is installed:

• Each door can operate independently.
• Rim exit devices latch into strikes mounted on the mullion.
• The mullion provides a secure latching point for both doors.
• The doors can be opened individually without removing the mullion.

When a wider opening is needed, the mullion can be released from its mounting hardware and removed.

Once removed, the center obstruction is eliminated, allowing the full width of the double-door opening to be used. This is particularly useful when moving large equipment, furniture, or materials through a doorway.

When the mullion is removed, the rim exit devices no longer have their normal latching points. Once the mullion is reinstalled and properly secured, the doors can latch into their designated strikes again.

What Is a Keyed Removable Mullion?

A keyed removable mullion is a type of removable mullion that uses a key-operated mechanism to release the mullion from its mounting hardware.

                         

Rather than requiring tools for removal, authorized personnel can use a key to unlock and release the mullion.

Keyed removable mullions are useful in commercial facilities where the full opening may need to be accessed regularly.

Benefits of a keyed removable mullion include:

• Convenient removal by authorized personnel.
• Controlled access to the mullion's release mechanism.
• Easier use of the full doorway opening when needed.

The exact removal and reinstallation process depends on the manufacturer and mullion model.

Removable Mullion vs. Fixed Mullion: What Is the Difference?

Although removable and fixed mullions both divide a double-door opening, they serve different purposes.

The primary difference is flexibility. A removable mullion allows the center post to be taken out when necessary, while a fixed mullion remains in place.

Removable Mullions and Rim Exit Devices

Removable mullions are commonly used with rim exit devices on pairs of commercial doors.

A rim exit device uses a latch at the edge of the door that engages with a strike. When a removable mullion is installed, each door's rim exit device latches into a strike mounted on the mullion, allowing the doors to operate independently.

This configuration provides secure latching while maintaining the option to remove the mullion when full-width access is needed.

For a closer look at different exit device configurations, read our guide on Rim Exit Device vs. Vertical Rod Exit Device: Which Do You Need?

Are Removable Mullions Used on Fire-Rated Doors?

Some removable mullions are specifically designed and listed for use in fire-rated door assemblies.

However, not every removable mullion is approved for a fire-rated opening.

When selecting a removable mullion for a fire-rated pair of doors, it is important to verify that the mullion, exit devices, strikes, and other hardware are compatible with the fire door assembly's listing.

Fire-rated applications may also require specific installation procedures and hardware configurations.

Always follow the manufacturer's instructions and applicable fire and building code requirements.

Final Thoughts

A removable mullion provides a practical solution for pairs of commercial doors that require secure latching while allowing occasional full-width access.

Understanding how removable mullions work and how they interact with rim exit devices can help building owners, contractors, and facility managers select the appropriate hardware for their openings.

At Beacon Commercial Door & Lock, we provide commercial doors, frames, and hardware for a variety of building applications. Selecting compatible components helps ensure proper door operation, security, and long-term performance.

Contact Beacon to discuss your project or request a quote.