The horizontal sliding accordion-type fire door is designed to respond to smoke detector activation, a fire alarm system, a manual pull station or in some instances even the activation of a sprinkler flow valve. Upon activation the door assembly will automatically begin closing. The building code permits a rate of closing speed not less than six inches and no more than 24 inches per second.

The Underwriters' Laboratories (UL) listing contains no limitations on the size of opening width and heights can be designed up to 23 feet. The typical assembly has separate listing from UL as a rated fire door assembly for 20 minutes, one hour, one and a half hours, and three hours. It also meets the UL 864 requirements for a smoke control assembly.

In terms of installation, the assembly can be designed in radial configurations and never needs a floor track, both features that increase design flexibility.

Lag Time in Awareness

The chief reason that horizontal sliding-door systems aren't used in more applications, manufacturers say, is that design professionals are not aware of the blanket acceptance of them in fire and building codes.

"There's always an audible gasp," said Welch, from Won-door. "I've had 100 design professionals in a room and there has not been the awareness that the the publication of the IBC in 2000 said, with a uniform voice, that you can use a sliding door in any application regardless of occupancy. It's unheard of. But enforcement officials felt the technology was better. If it was just as good as a swinging door, there would be no reason to make a code change."

The International Building Code is clear on the subject. In Section 1008.1.2, the code states that "egress doors shall be side-hinged and swinging," but the fifth exception is this: "In other than Group H occupancies, horizontal sliding doors complying with Section 1008.1.3.3 are permitted in a means of egress."

Section 1008.1.3.3 of the International Building Code requires that the horizontal door systems:

• Shall be power operated and shall be capable of being operated manually in the event of a power failure;
• Shall be openable by a simple method from both sides without special knowledge or effort;
• The force required to operate the door shall not exceed 30 pounds…to set the door in motion and 15 pounds…to close the door or open it to the minimum required width;
• The door shall be openable with a force not to exceed 15 pounds… when a force of 250 pounds…is applied perpendicular to the door adjacent to the operating device;
• The door assembly shall comply with the applicable fire protection rating and, where rated, shall be self-closing or automatic closing by smoke detection, shall be installed in accordance with NFPA 80 and shall comply with Section 715;
• The door assembly shall have an integrated standby power supply;
• The door assembly power supply shall be electrically supervised;
• The door shall open to the minimum required width within 10 seconds after activation of the operating device.