Canadian Consulting Engineer

Automatically Speaking

May 1, 2004
By Kevin Cheong, P.Eng.

Buildings have access control systems to prevent unauthorized people from entering while at the same time providing simple access to legitimate users.

Buildings have access control systems to prevent unauthorized people from entering while at the same time providing simple access to legitimate users.

Commonly, mechanical locks or electronic locks are used to accomplish these goals. Electronic locking systems have advantages because they can relatively easily be made to identify unique individuals (without resorting to biometric systems) and can easily provide data logging of who accessed, or attempted to access, a lock. More importantly, electronic systems can be disabled relatively easily if someone loses their access device. It is far harder to control keys and punch codes for mechanical locks. Also, mechanical systems can’t remember which keys have been used and when.

Access can be electronically controlled i.e. doors are locked, by a number of means. However, not all electronic methods are looked upon equally by the building codes. Building code officials are sometimes hesitant to approve electronic solutions when they’re not specifically mentioned in the codes. Their distrust may be due to concerns about events like power failures. Yet in an outage, the hardware can be designed to go into a failsafe mode and begins to work mechanically like regular door hardware. The most important thing is that the building’s access system is automatically monitored for failure and is maintained properly.

It seems that current code requirements in Canada are lagging behind new developments in technology, which makes it difficult for designers to meet the needs of the building and its users. Following are some of the trickiest and most ambiguous areas related to what codes allow and disallow for door access locks.

Trouble spots

The National Building Code of Canada1 (NBC) allows for simple mechanical locking based on keys, or specialized devices, or knowledge (presumably cardkeys or memorized access codes). The NBC also covers simple door hardware like self-closers, hold-opens, door knobs, levers, paddles, and panic hardware.

Mag-Locks. The code recognizes electro-magnetic locks2 (mag-locks) — but only when they are applied in a specific way that is rarely fully complied with.

In particular, it is rare in practice that a door with a mag-lock releases within 15 seconds of a 90 Newton force being applied. It is even more rare that the mag-lock will release even if only pressed momentarily, or that the release is irreversible, i.e. that the mag-lock requires the door to be opened before it can be relocked, and that the lock can only be manually re-engaged again using a switch. These conditions are all required by the code, but to implement them can be extremely expensive — up to $4,500 per door when you take in all the power infrastructure, etc.

Electric Strikes. The code does not mention electric strikes by name, but we can comply with the code by using electric hinged lip strikes (where the lip that holds the latchbolt pivots out of the frame to release the door) and motorized strikes (pistons concealed in the latch pocket).

The reason electric strikes can comply with the code whereas other solutions may not, is that they work in conjunction with simple mechanical locking hardware. They permit latching when the door is closed, and they permit electronically controlled access without the physical need to unlock the hardware. Opening a door with simple mechanical locks typically requires inserting a key into the lock itself, whereas an electric strike can release the door by simply releasing the latch bolt.

It is, however, often difficult to maintain the fire rated listing of a door and frame assembly if the frame is modified by the subsequent installation of an electric strike. Unfortunately it is probably rare to have a door and frame including an electric strike listed by Underwriters Laboratories.

Controlled Egress and Dogging. The code does not seem to fully allow for innovations such as automatic dogging. Dogged latches are held in the retracted position, leaving a door free to swing open or closed during normal operations. With electronic dogging, the latch is retracted automatically and only released to hold the door closed during a fire.

Current codes do allow dogging when the door is not located in a fire separation. For example, mechanical dogging is used in the front door of a school where a standard latch would be quickly worn down through over-use. However, for the same school project, the code won’t allow the doors to the stairwells from the entry hall to be dogged because they are part of a fire separation (although they may be put on hold-opens if the building is not more than three storeys3).

Despite the code requirements, the automatic retraction of the latch, and automatic re-engagement after each operation is common practice when double doors in fire separations are equipped with door openers. The vertical rods are retracted when the door is opened and released when the door recloses.

Nor does the code recognize controlled exit (delayed egress) fire exit hardware. Yet this equipment is often a good idea for secure environments. The code does allow for some exemptions. Examples are for “impeded egress”4 situations (a building code defined term meaning occupants are restricted to a group of rooms), and for “contained use,” (where occupants are restricted to a single room).

However, officials don’t always interpret the exemptions in the code as fully applicable. In particular, they don’t always believe that impeded egress areas are exempted from the restrictions on the use of mag-locks. While some jurisdictions feel the requirement to release the doors within 15 seconds of a 90 Newton force being applied obviously shouldn’t apply in an impeded egress situation, others feel that the restrictions on mag-locks apply to any application.

One of the applications where the requirements — and the limitations of the code — are tested is in dementia (Alzheimer) wards in hospitals. The wards are often designated impeded egress zones for the protection of wandering patients. How do you impede egress, while complying with the requirements of the code that occupants be able to exit the building readily in a fire or emergency? One alternative that meets code is simply to have mechanical key locks on either side of the door. Each door would have to be manually released in the event of an emergency.

The second alternative is to use remote release hardware that is accessible to security personnel, augmented with fire alarm release. Typically this means some form of electro-mechanical or electro-magnetic lock or releasing hardware. Often, though, we are dealing with existing facilities with doors that have simple doorknobs. As noted above, if we use electric strikes, we violate the fire rated listing of the door and frame assembly.

Ironically, therefore, we can comply with the building code by mechanically locking an exit door even though it means potentially leaving it locked during an emergency, but we cannot always use mag-locks that will release automatically, unless we also allow patients to leave within 15 seconds of applying a 90 Newton force on the door releasing hardware. Not only that, but the release must be irreversible and manually reset. If we attempt to use other electro-mechanical hardware, building officials are unsure how to treat it because it is not discussed in the code.

Some answers

One type of hardware we are currently working with uses a magnet to prevent the push bar in an otherwise standard panic set from depressing fully for the 15 seconds noted above. A lever and cam type assembly is connected between the magnet and the push bar, but the magnet does not lock the door itself. We do not consider this to be an electromagnetic lock because the electromagnet does not lock the door — the latch on the panic set locks the door. If we propose these devices as electromechanical hardware, the code prevents their use because they are not “readily openable.” They are not electromagnetic locks, but we are compelled to treat them as such because their use is otherwise prevented. We feel they are superi
or to electromagnetic locks for many applications because they restrict access sufficiently to deter indiscriminate use without requiring unusual modifications to a listed door and frame assembly. Also they don’t apply force to the door corner, avoiding the problem of the door ending up so warped that it won’t latch or seal when necessary.

People often assume that access control and intrusion detection are the same thing, but they are two different components of a security system. Intrusion detection seeks to detect unauthorized access and generally triggers an alarm system. It is intended usually to detect forced entry. We have worked on card access systems that do not have alarming for forced entry in situations where there are a relatively large number of people coming into work at odd hours and a lack of personnel to monitor the system. An access control system does log user access and forced entry, but only for historical purposes.

Finally, electronic access control is unfortunately often based on relatively proprietary systems, but this does not need to be the case. Much of a system can in fact be open to competition, or best-of-breed selection. Often, the reason proprietary systems are used is that project leaders leave it to a limited number of individuals to specify the entire system and those individuals for their own comfort level tend to focus on single source suppliers with which they are familiar. What many people fail to realize about access systems is that generally only the device carried by the user and the portion that recognizes it — for example, the key and cylinder that the key fits into, or the card and the card reader and its associated controller — need to be at all proprietary.

Innovative solutions to code challenges are often met with resistance, but designers and product manufacturers will always be compelled to develop “the better mouse-trap.” As the codes change, hopefully authorities will recognize the preferred solutions.

Kevin Cheong, P.Eng. is a project manager with Stantec Consulting in Vancouver.

1 National Building Code of Canada, (door latches), hardware), (fire fighting access), and release hardware)



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