As the Door Turns

A Retrofit Saga

by Robert L. Pearson, PE

Access control is a continuing concern of security managers. Some effective methods are simple, such as a solid door with key locks, and some methods are more elaborate, such as computer systems that evaluate the credibility of the person seeking admission. Many levels of access control fall between these two extremes.

 The different levels of access control are determined by the electronic complexity of the components, not the degree of security they can provide. One method does not necessarily ensure a higher degree of security just because it is more complex. One type of control is only better than another in the sense that it may be more appropriate for a given use. A key lock is perfectly satisfactory when card access is unnecessary.

One technique for access control is a two-door system, or mantrap. Hofmeister and Prince, authors of The Security Dictionary (Howard W. Sams & Co., Inc., Indianapolis, IN, 1983), define a mantrap as a booth with two or more remotely controlled doors that an individual must pass through. Persons unable to produce proper identification are not allowed to pass and may be detained. A mantrap can be regulated by several different access control techniques.

Mantraps were no
longer the answer.

At Texas Instruments in Dallas, TX, we had installed twenty-four mantraps in six buildings. Thousands of employees used them. The mantraps had the following features:

After several years of use, we decided the mantraps had become ineffective as access control for our facility. Besides the number of human operators required to control the doors, the mantrap system was limited for a number of reasons:

• No documentation was available on the identification of a person or the time or location of his or her entry or exit.
• Security personnel were delayed in responding to the twenty-four different entrances.
• Maintaining a high resolution CCTV scene so employees could be recognized was difficult.
• Slowing employees' entrances and exits so they and their badges could be recognized and matched was a problem.
• An expired or "lost" badge might gain a person illegitimate access to the building.
• Shift changes required additional personnel to operate the doors because many people had to move through them in a short time.

Because of these problems we decided to alter our approach to access control. We considered upgrading our access control system to a higher level, but none seemed feasible. Finally, we decided that a physical change, rather than additional electronic complexity, would improve our system and be more cost-effective. Our solution was to replace mantraps with revolving doors.

Testing the Change

To test our plan, we placed a turnstile adjacent to an exterior mantrap at one building (Building X). This particular mantrap had a relatively low volume of traffic. After a short while employees were using the turnstile instead of the mantrap. For aesthetic reasons, we then decided a revolving door would be preferable to the turnstile. Two revolving doors were installed in Building X as prototypes. Later, five more doors were added. More than 10,000 employees pass through these seven revolving doors daily. Building X previously had used three mantraps for entry and exit.

The two original experimental doors were motorized and started to turn as soon as an employee's badge was successfully read by a card reader. They had four leaves with an opening size of 6' 6" (see Exhibit 1), and they had elaborate motion detectors to verify that only one person was in the door.

The motorized revolving doors begin to turn as soon as the vertical card reader successfully scans an employee's badge.

These experimental revolving doors were used for about a year before we decided to install revolving doors at all entrances. We had several questions to answer before our decision became final:

• Should the doors be motorized?
• Should the door have three leaves or four leaves?
• What should be the opening size between the leaves?
• How should the leaves be situated when the door is idle?
• What type of detection should be used to verify that only one person is in the door to prevent "piggybacking?"
• Where should the badge reader be placed, and what visual indicators should it use?

After our security staff decided exactly what we wanted, we formed a team who went to a revolving door manufacturer to agree on door criteria. The manufacturer designed the revolving doors according to our specifications. Since then, a revised version of our door has become part of the manufacturer's standard product line. The door specifications and the reasons behind the specifications are listed in Exhibit 2.

Exhibit 2 Final Revolving Door Specifications
Specification	Reason
Power-assisted door	To provide motorization and to allow the door to be pushed at a faster rate if necessary
Four door leaves	To permit only one person at a time in the door
Door opening size of 6'6"	To meet local fire regulations
Door leaves stop perpendicular to opening	To provide a smaller opening to prevent piggybacking; The door only needs to rotate ninety degrees, which provides less wear and tear and improved traffic flow
Floor mats for detection of person in booth	To provide a very reliable and simple method of detection
Segmented sides of the door	To eliminate a need for expensive curved glass and to allow use of tempered glass
Adjustable rotation speed	To allow flexibility
Safety sensor on edge of side wall and pressure sensor at base of leaves	To protect against getting an arm caught between the edge of the door and a leaf as well as to protect against bumping someone in the door
Safety guard at bottom of door leaves	To prevent door traveling over one's toe before stopping
Capable of being freerunning via a motion detector	To allow 8am to 5pm free entrance and exit to and from a staffed lobby
Weatherstripping of leaves	To provide weather protection in case the door is used on an exterior wall
Relay activation from an outside source	To allow present badge reader system to control doors
Collapsible leaves	To meet fire code regulations
Bidirectional traffic flow	To reduce delays in processing people

An in-house architect was called on to specify the anodized color finish and the segmented glass or round metal for the canopy, depending on the location (see Exhibit 3). He also designed the standard entrance area to include six-foot-high emergency exits.

The revolving doors were set inside the building with a vestibule between them and the outside. This installation is energy efficient and gives employees a waiting area out of the weather.

In Search of Bogus Badges

Despite all our planning, we still did not foresee some of the difficulties that lay ahead, specifically problems with retrofitting. To add to the task, we had buildings with large numbers of employees. Shift changes would present problems, and the doors would probably be perceived by employees as an irritant. Another potential problem was that employees' current badges might not work on the badge reader system, since badge reader entry was not plant-wide. Some employees had used badge readers, while others had only used mantraps and lobby entrances.

At Texas Instruments our picture badges are made on site with a Weigand strip for identification details. Although everyone's badge could be read, and many badge readers were already being used, not everyone had used their badges to gain entry. We were uncertain about the integrity of the badges: Were employees properly in the card reader's computer base? Had the badges’ physical composition deteriorated so they were unusable? Unfortunately, the answers to both of these questions were "yes."

In order for us to determine where problems might arise, several badge testers were built at major entrances to Building X, our test site. The testers were comprised of a badge reader, a green light (good badge in the computer), and a red light (badge not good or not in the computer). The reader head and lights were mounted on a movable stand. To help employees understand the changes that were taking place, an announcement concerning the new access system was distributed. An excerpt of this announcement is given in Exhibit 4.

---

Exhibit 4

Use of New Security Access Control for Revolving Doors

The upgrade in security access control for the building is proceeding with installation of a badge access controlled, revolving door at the lobby entrance. Construction is now underway on a revolving door for the southwest entrance to the building, with a third door scheduled for installation at the southeast entrance.

Employees who have not yet verified that their badges will work properly with the new doors should check them on the lobby door or the trial badge readers near the southeast and southwest entrances. This will identify any badge problems that may exist and prevent any inconvenience to you after the doors are installed.

Questions concerning badge problems should be referred to the security badge room, which is adjacent to the health center, or call 000-0000.

The revolving doors can be used at any time by any employee with a valid badge. The procedure for using the door is as follows:

1. Slide your badge downward through the card reader. The badge photo should face the side of the card reader marked picture.

2. Check to be sure the green light is on.

3. Step onto the black mat in the revolving door in the space between the badge reader and the glass door.

4. The door will then start to revolve.

Material moved on carts and dollies through the southeast entrance will continue to use this area after construction of the revolving doors is complete. A single door with an automatic opener will be available for personnel with disabilities and material movement by personnel with extended material passes. One-day passes and special access needs will be processed through the lobby. Questions concerning material movement should be referred to physical security at 000-0000.

---

The badge testers were left in place even during construction. We found that many people would test their badges only after an entrance was under construction. A guard would be at an emergency entrance adjacent to the entrance under construction to verify that the people entering were employees. Seeing the familiar entrance closed and a guard verifying the credentials of those who pass there made employees realize that if their badges were not working on the system they would not be able to get into the building when construction was completed.

It Only Takes Five Seconds

Prior to beginning construction, we checked affected entrances for people flow. The number of people using an entrance was counted to determine whether the revolving doors could handle the flow. The revolving doors were tested, and we determined that five seconds per person was a reasonable time for entrance or exit. It is possible to reduce this time if employees are familiar with the system; however, to allow for glitches such as someone dropping his or her badge, improper badge use in the reader, or other problems, we set an average time at five seconds. If the volume of traffic was heavy enough to require the use of another door, it would be added. At our heaviest traffic entering Building X, two doors were used and still, during one ten-minute period, the doors could not handle the traffic flow using the five-second criteria. We decided just to live with this ten-minute vulnerability.

We noticed when we were testing the prototype revolving doors that people pace themselves according to the congestion at the doors. If the door is unoccupied, they walk a little faster; if occupied, they slow down. Since most of the buildings have long hallways leading to the doors, this self-regulation has been effective.

Finally, the big day came for the first doors to be used. A guard was ready at the door to instruct the first shift of employees on how the door operates. A technician was also at the door by 7:00 am in the event of any mechanical problems. With all this planning, we felt the situation was under control.

Unfortunately, we were wrong. The first three days were complete chaos. People were apprehensive and easily embarrassed as they tried to use the doors. Some people still had not tested their badges, and some forgot their badges, but the largest problem was the lack of employee familiarity with the combination badge reader/revolving door operation.

After three days employees became more accustomed to the system. Badge problems were fewer. Nevertheless, guard and technician support continued throughout the first week.

Week number two saw even more improvement. People knew how to use the doors and the traffic flow increased substantially.

The system allows people to have their badges read before another person in the door has reached the other side. When this happens, the doors appear to be turning continuously, increasing traffic flow to a maximum of one person every two-and-a-half seconds. The doors have badge readers on both sides so people can come and go in opposite directions at the same time.

To help employees understand what was happening when they slid the badge through the reader, a green light was mounted with the reader to let them know when and if their badge was accepted. An assistance button was also mounted above the reader to initiate communication with the security control center. The reader, the light, and the button were mounted on a beveled plate about sixty inches from the floor.

A CCTV camera was mounted on the interior of the buildings to view the doors. This view made it easier for security officers to help employees and also allowed them to see what was being carried into and out of the building. The spacing between the leaves was restricted but would not prevent carrying a briefcase or small package. These cameras record events, and the tapes are reviewed when necessary.

Day-to-day operations problems were quickly solved. One obvious problem was the need to move ladders and other maintenance items in and out of the building. To handle these exceptions, all facilities-related needs are now processed at the loading dock. Salespeople, visitors, maintenance workers, and people with disabilities are required to enter and exit through the lobby.

In summary, I would say the revolving doors have performed as expected. After the initial changeover very few mechanical or electrical problems remain. Within the first month of operation the problems had almost disappeared.

The change of an existing building from mantraps with unrestricted entrance and exit at shift changes to revolving doors with badge readers was a major challenge for everyone. By using revolving doors instead of mantraps, we expect to reduce the number of people needed in the security control center from two operators twenty-four hours a day, seven days a week, to one operator ten hours a day, five days a week, and eventually, to no operator. Shift coverage will also be eliminated.

We are now planning to use revolving doors for access control within buildings. There is also one installation in progress for a restricted area that uses revolving doors with tinted glass.

When considering the use of revolving doors, I would recommend a thorough investigation of the fire codes for your locale. One of three fire codes may apply: the Uniform Building Code, the National Fire Prevention Association (NFPA) Code, and the Standard Building Code (SBC), or some modification of these. Only NFPA has allowed for security revolving doors. The other codes do not recognize revolving doors as points of egress.

PICTURE THIS BIG CITY SCENE: The trench-coated businessperson, briefcase in hand, comes running through the lobby of a posh building, pushes through the glass revolving doors, quickly hails a cab, and rushes off to his or her next destination. Now, however, revolving doors don't rotate just in glamorous hotels or corporate megastructures. One of the newest applications for revolving doors, or revolvers as they are known in the trade, is for access control. Revolving doors proved to be just the ticket when three different airports -- Daytona Beach, FL; Mobile, AL; and San Juan, Puerto Rico -- were looking for security alternatives.

Daytona Beach, Florida

After a would-be hijacker walked onto the runway and boarded a Delta DC-9 at the Daytona Beach Regional Airport in March 1986, the security department decided to turn the unpleasant situation around -- literally. The hijacker had entered the restricted area by walking the wrong way through automatic swinging doors. Joel Watkins, chief of airport police at Daytona Beach, quickly began researching security systems appropriate for the Daytona Beach airport. His solution for runway access control was one-way revolving security doors.

Watkins wanted to find a security system that would allow passengers to deplane easily but would still act as a physical barrier to restrict unauthorized pedestrians. He was familiar with the use of revolvers at TWA's International Terminal A at JFK Airport in New York City. In August 1985, TWA had installed two automatic, one-way revolving doors to provide barrier-free exits from its arrival gates. The doors also provided a restricted entrance for departing passengers.

After visiting the installation at JFK, Watkins contacted Horton Automatics, the door manufacturer. Horton recommended one nine-foot, three-wing, automatic revolving door at each entrance to the secure areas in both the main and east terminals at Daytona Beach. Like the TWA installation, arriving passengers from all carriers would be guided by signs through the revolving doors and on toward the main terminal area. Signs would also instruct departing passengers to bypass the doors and walk through the X-ray security system.

The revolving doors are part of a triple-layered security system for the Daytona Beach Regional Airport. The three-wing security doors are first protected by microwave motion detectors that sense when a person approaches the corridor from the wrong direction. This early warning detection system deters the errant passenger with a voice annunciator that says, "Security violation; please exit." Should the person continue down the corridor and try to enter the door from the wrong side, a switch in the floor mat closes a contact and slowly stops the door. The door will then reverse and try to "back out" the person. If the person resists the backward motion, the door automatically locks into place.

The third aspect of the triple-layered system involves airport security police. If either door locks into place, a covert alarm system activates the beepers carried by all airport police. The beepers announce a security violation and identify the door involved. At this point, police investigate.

Mobile, Alabama

When the Mobile airport moved into its new terminal building in November 1986, Charles Moore, chief of airport police, was there to oversee the operation of three new one-way revolving doors. "There were a few snags," reports Moore, "but essentially all we've had to do is watch the doors operate and then adjust them so they become as convenient and safe as we can make them." Since installation, Moore has adjusted the rotation speed of the doors "to suit as many people as we can." Moore also reasoned that passengers would be less likely to try to push the doors if they saw them rotating as they approached. Microwave motion detectors, which control when the doors rotate, were adjusted so that rotation begins when passengers are about fifteen feet from the doors.

Two security revolving doors were installed at the main concourse, which serves all carriers, and one door was installed at the Continental Express deplaning area. The main concourse revolvers are used by deplaning passengers moving from the secure concourse to the public lobby.

The revolving doors are located on either side of an X-ray screening device and are not staffed by security personnel, but they can be seen by an airport police officer at the screening point. Also, the doors are monitored by CCTV.

If a passenger attempts to step into the door from the wrong side while it is rotating, the door stops immediately. A voice annunciator warns, "Wrong way; please exit," and the door begins slowly to nudge the intruder out. If a passenger falls or bumps against the safety edge or onto the door itself, the door automatically stops. To secure the system further, an alarm rings in the central security office if the door loses electrical power.

San Juan, Puerto Rico

One-way revolving doors have also been adapted for use at large airports. Joseph Kuhlmann of Omniplan Architects in Dallas, TX, specified five revolving doors for American Airlines' terminal expansion at the Louis Munoz Marin International Airport in San Juan, Puerto Rico.

Omniplan designed the new terminal wing, which includes nine gates for American Airlines and eleven parking positions for airplanes operated by American Eagle, a feeder line. The terminal expansion was completed in stages. Two pairs of revolving doors have been in operation since November 1, 1986; the fifth door went into service on January 15, 1987.

Kuhlmann specified the revolvers primarily to control the flow of people in secure areas of the terminal. All the revolvers are located at the ends of corridors that funnel deplaning passengers from secured areas like customs and immigration to unsecured baggage areas. Like the TWA/JFK installation, passengers who attempt to enter a restricted area by coming through the doors in the wrong direction are advised by a voice annunciator to exit. Signs direct arriving passengers to exit through the doors.

The three-wing automatic doors are activated by a microwave motion detector that identifies passengers ten feet in front of the door. The doors revolve at six revolutions per minute, but the touch of a button will slow the door to two revolutions per minute to accommodate passengers with disabilities.

Other safety devices include a switch that stops the door automatically if a passenger falls or bumps against it and a side swinging door with a panic device for emergencies. In case of a power failure the automatic door can also be operated manually. A signal will notify security personnel of this condition.

Horton doors are designed differently from other revolving doors. The round door enclosure is constructed of eight flat, glass panels instead of three pieces of curved glass. The panels are set at an angle to conform to the rotation of the door and secured in extruded aluminum rails. The rails extend through the canopy and form a segmented canopy design.

Being able to specify flat rather than curved glass allowed Kuhlmann to reduce the cost of the glass by 30 percent and the delivery time by several weeks. Curved glass is expensive, must be special ordered, and often requires a four-to-six week lead-time. In most instances, flat glass is available off the shelf.

Unlike his counterparts in Daytona Beach and Mobile, American Air-lines' Construction Project Manager Frank Esposito in San Juan is concerned with processing a lot of passengers -- more than 100,000 every month -- through the revolving doors. Though beefing up security by adding more officers was considered, Esposito believes the decision to automate this aspect of his security system was the better choice. Esposito says, "The doors look very professional, and they provide round-the-clock, consistent traffic control. Any security system has to be viewed as a deterrent, not as foolproof, but one-way revolvers are the best we can do to secure this airport."

About the Author . . .

Robert L. Pearson, PE, is manager of electronic security systems, Texas instruments, Dallas, TX. He has designed security systems for the Department of Energy at nuclear weapon sites and consulted for the strategic oil reserve. Pearson was formerly responsible for security electronics and energy management systems at Mesa Petroleum. He is a member of ASIS.

Reprinted from the June 1987 issue of Security Management. American Society for Industrial Security, 1655 North Fort Myer Drive, Suite 1200, Arlington, VA 22209.