Security of the entrance to the premises: vestibule-airlocks.

Security of the entrance to the premises: vestibule-airlocks.

Glazov Evgeny Aleksandrovich

SECURITY OF THE ENTRANCE TO THE PREMISES: VESTIBLE-AIRLOCKS

Source: magazine «Special Equipment»

Currently, there are various ways to protect the entrance to the protected premises: simple and reinforced doors, wickets, three-bar turnstiles (tripods), half-height and full-height turnstiles, automated checkpoints, airlock cabins (vestibule-airlocks).

All the devices listed above can be used both independently and in integration with access control systems (ACS). However, most of these devices do not completely eliminate unauthorized passage.

For example, doors and gates do not ensure separation of the flow of people passing through. A person who has the right of access to the relevant premises through a door or gate can not only pass through himself, but also let in an arbitrary number of people. In this case, it is impossible to control the direction of passage.

Various types of turnstiles and automated checkpoints allow people to pass “one by one” and control the direction of passage. However, all these devices, with the exception of full-height turnstiles and airlock cabins, have a relatively low level of protection against unauthorized entry into the facility.

This is due to the fact that the barriers of a tripod, half-height turnstile, as well as an automated checkpoint can be overcome by intruders quite easily. In this case, ensuring the safety of the facility falls on the security staff.

Vestibules and full-height turnstiles provide for the closure of the entire passage area, with the controlled passage remaining permanently closed by one of the doors of the vestibule or one of the blades of the full-height turnstile.

Vestibule-airlock is a structure consisting of two successively opening doors. A special control circuit ensures that under no circumstances, except in emergency evacuation mode, are both doors of the airlock opened simultaneously.

Thus, the entrance to and exit from the premises remain permanently closed to unauthorized entry into the facility.

Doors and other elements of the airlock structure are usually made of bulletproof or penetration-resistant materials, which ensures protection of the premises from forced entry and terrorist attacks.

In addition, various devices can be built into the design of airlock cabins that monitor people passing through for items prohibited for carrying — weapons, radioactive substances and explosives. When these items are detected, the logic controlling the airlock issues a signal prohibiting passage through the vestibule, or blocks the intruder inside the airlock.

The entire range of airlock cabin models can be divided into automatic and semi-automatic airlocks.

In automatic airlocks, doors are opened and closed using various electromechanical drives controlled by airlock logic. In semi-automatic airlocks, conventional swing doors are used, opened manually and closed by closers. Airlock logic in semi-automatic booths controls electromechanical or electromagnetic locks.

In addition to these two main types of booths, companies specializing in the production of airlock vestibules, as a rule, manufacture booths with revolving doors, combining the features of full-height turnstiles and automatic airlocks.

TEDRIA semi-automatic airlock vestibules

The simplest semi-automatic airlock is a booth with two swing doors at the entrance and exit.

Each door is equipped with a door closer and a lock (electromechanical or electromagnetic). The locks of both doors are controlled by a common gateway logic, which ensures that the two doors are not open at the same time.

In the simplest case, reed switches are used to control the state of the doors (closed/open). In addition, semi-automatic cabins often use electromechanical locks with a built-in lock state sensor (locked/open).

In this case, the gateway logic considers the door closed only if two signals are present simultaneously: “closed” from the reed switch and “locked” from the lock sensor. The semi-automatic gateway can operate in manual or automatic modes.

In manual mode, commands to open the doors are sent to the gateway logic from the control panel installed at the security post.

In this case, the decision to allow passage is made by security personnel. To obtain information about the visitor, the airlock can be equipped with an intercom and/or a television surveillance device.

In order for security personnel to be able to observe the visitor inside the airlock cabin, an additional video camera is used, which is placed inside the airlock.

In addition, in most cases, semi-automatic cabins are a metal structure with doors and side walls made of bulletproof or bulletproof glass.

The doors and side walls can be glazed completely or partially.

In addition to opening the doors one by one, security personnel have the ability to unlock both doors simultaneously using the remote control.

This is necessary to ensure unimpeded exit of people from the building during an emergency evacuation or if it is necessary to carry large objects through the airlock.

In automatic mode, the decision to allow passage through the airlock is made without the participation of security personnel.

In the simplest case, the permission signal to the gateway logic can come from the human presence sensor in front of the cabin.

However, in most cases, an access control system (ACS) is used to control the gateway logic in automatic mode.

In the ACS, various personal identifiers can be used to make a decision on permission to pass: magnetic card readers, Weigand cards, contactless radio frequency (proximity) cards, keyboards, various biometric identifiers, etc.

Using the ACS allows not only to allow access to the protected facility to various categories of employees and visitors only at certain hours and days, but also to record events and work time.

In automatic mode, the gateway logic, having received a signal to allow access, checks whether the previous passage cycle has been completed.

Only after this is the lock of the first door unlocked. Then the gateway logic monitors the closing of the first door and the presence of a person inside the cabin (for example, using a passive infrared sensor).

If, within a specified time interval, usually several tens of seconds, the gateway logic does not receive a signal that a person has entered the cabin, the cycle is considered complete and the second door does not open, and the gateway logic switches to the waiting mode for the next signal to allow passage.

If a person enters the cabin and the first door closes, the gateway logic, depending on the specified operating algorithm, either issues a command to unlock the second door or waits for an additional permission signal from the ACS. To generate this signal, the ACS must receive confirmation from an additional identifier installed inside the cabin.

For example, a magnetic or proximity card reader can be used to enter the gateway, and as an additional identifier, a keyboard for entering the individual code of the owner of the presented card, or a biometric identifier, is usually located inside the cabin. Such an organization of the gateway in automatic mode allows to exclude passage with a stolen or lost card.

When using an additional identifier, having received a permission signal from the ACS, the gateway logic gives a command to unlock the lock of the second door.

If, however, no additional permission signal is received from the ACS within a specified period of time, then the gateway logic, depending on the specified algorithm, either unlocks the lock of the first door and issues a voice message asking the intruder to leave the cabin, or locks the intruder inside the cabin and waits for further commands from the control panel or from the ACS.

When the gateway operates in automatic mode under the control of the access control system, one or more people may pass through the gateway together with the person who has the right of access to the facility. In addition, a terrorist with a hostage who has the right of access may pass through the gateway. To prevent these situations, various systems of control of passage “one by one” are used in gateway cabins. In semi-automatic gateways, various capacitive and contact mats, infrared and microwave sensors, weighing systems are used as sensors of these systems. However, all these systems have their drawbacks and in some cases do not allow control of passage “one by one”.

The best results are achieved by using a weighing system in combination with the ACS. In this case, the weight of a person inside the cabin is compared with the corresponding value from the ACS database. This method, which allows for complete control over the passage through the airlock “one by one”, is, however, more often used not in semi-automatic vestibules, but in some models of automatic airlock cabins.

Sometimes, purely mechanical solutions are used in semi-automatic vestibules, allowing only one person to pass through the airlock.

For example, the UNIVERSAL 2000 airlock from the Swiss company Scheebrli uses folding deflectors that rise to a horizontal position after a person has entered the airlock (Fig. 1).

The disadvantage of these systems is the inconvenience of passage through the cabin, especially for large people.

Fig. 1 UNIVERSAL 2000 gateway

In addition to the problem of controlling passage “one by one”, there are difficulties in installing metal detectors (MD) inside semi-automatic gateways.

There are two main types of metal detectors: dynamic and static. Dynamic MD react only to moving metal objects, and static ones to both moving and stationary ones.

Most MDs produced in the world are dynamic. Dynamic MDs, having good resistance to external electromagnetic interference, have high sensitivity to large masses of metal moving nearby.

Therefore, when installing a dynamic MD inside a semi-automatic cabin with swing doors that have a metal panel or metal frame, the MD will give false alarm signals when the door moves. If the MD is blocked while the entrance door is closing, then an intruder with a weapon will pass through the MD frame during the door closing and stop, and the dynamic MD will no longer respond to a stationary metal object.

Static metal detectors allow you to wait until the entrance door closes, after which they check for weapons on a person inside the cabin, even if he is standing still.

For this, the MD frame is made for the entire depth of the gateway. This solution is used in gateway cabins produced by some Italian companies (CESCU, MUZIO, PROGETECH).

The disadvantage of this solution is the high sensitivity of static MD to external electromagnetic interference, which complicates the use of such gateways at many sites. Another solution, implemented, for example, in the semi-automatic gateways «TEDRIA» manufactured by the Italian company SECOD, is the manufacture of the gateway entrance door practically without the use of metal parts. The door frame in which the bulletproof glass is installed is made of special composite materials, the electromechanical lock is installed not in the door frame, but in the jamb, the door handles are made of plastic, etc.

Thanks to these design solutions, a constantly operating dynamic MD is installed in the immediate vicinity of the entrance door. In this case, the MD reacts to the presence of a weapon on a person entering the airlock and does not give false alarms when the door moves.

The advantage of semi-automatic airlocks is their relatively low cost, the disadvantages include low throughput and the need to apply significant force when opening doors equipped with heavy armored glass.

SIRIO automatic vestibule-airlocks

The main distinguishing feature of automatic vestibules is that their doors open and close using electromechanical drives. This makes them much easier to use and increases the throughput capacity of the gateways.

The gateway logic in automatic cabins controls door drives rather than locks. An automatic gateway may have single-leaf or double-leaf swing doors; folding doors; single-leaf or double-leaf sliding doors with flat or semicircular leaves, cylindrical doors; single-leaf and double-leaf doors with flat rotating leaves.

There are automatic gateways with two doors of different types, as well as combined gateways, one of the doors of which has an electromechanical drive, the other does not.

The simplest in terms of engineering solutions are automatic gateways with swing doors. They differ from semi-automatic gateways in that instead of a closer, an electromechanical drive is installed on the door.

However, an automatically opening swing door can hit a person standing in front of it, and the use of special protective sensors only partially solves the problem, since this significantly reduces the actual throughput of the gateway — a person in the door's movement zone prevents it from opening and closing.

Automatic vestibules with flat sliding doors do not have this drawback. In these cabins, the doors, which have one or two leaves, are moved to the side by means of drives (Fig. 2).

Fig. 2. Airlock with single-leaf sliding doors

Automatic airlocks with flat sliding doors have a higher throughput capacity than airlocks with hinged doors, but their external dimensions significantly exceed the dimensions of airlocks of other models with the same passage width.

This is explained by the fact that in an airlock with flat sliding doors, there must be space on the side of the passage into which the doors enter when they are opened.

To ensure the best “passage width/cabin width” ratio, double-leaf doors are used, in which both doors move in the same direction (Fig. 3).

Fig. 3. Airlock with double-leaf doors

This ratio is even better for TELESCOPICA DOPPIA cabins from SECOD and MULTITRANSITO cabins from SAIMA, which are two independently operating airlocks combined into one design (Fig. 4)

Fig. 4. TELESCOPICA DOPPIA airlock

Vestibules with folding doors (Fig. 5) and cabins with rotating flaps have good throughput and “passage width/cabin width” ratios.

However, the use of dynamic metal detectors in these locks is difficult for the same reasons as in semi-automatic cabins.

Fig. 5. Lock with folding doors

Some Italian manufacturers (MUZIO, CESCU, PROGETECH) produce airlock cabins with double-leaf doors with flat rotating flaps, which use static-type metal detectors (Fig. 6).

The advantage of these cabins is a very good ratio of “passage width/cabin width”, and the disadvantage is the difficulty of setting up a static metal detector in the presence of external electromagnetic interference.

The most widespread are automatic vestibule-airlocks with sliding semicircular doors (Fig. 7).

Models of this type are produced by almost all European manufacturers of airlock cabins.

Fig. 7. Gateway with semicircular sliding doors

Automatic gateways with semicircular sliding doors can have both single-leaf and double-leaf doors. Most models from Italian manufacturers can be equipped with a built-in dynamic metal detector, since all moving metal parts of the drives are located above the passage area.

The “one-by-one” passage control system in automatic gateways of this type is most often implemented on the basis of a weighing system.

An airlock in which the weighing system only controls the cabin floor allows an intruder with a weapon to pass through it, despite the built-in dynamic metal detector. This is explained by the fact that the dynamic metal detector gives an alarm signal when the intruder passes through the entrance door.

In this case, the second door does not open, and the speech synthesizer gives a message demanding to leave the cabin.

The intruder can attach a weapon to the interior walls or ceiling of the cabin, exit the airlock and re-enter it. In this case, the second time he passes through the metal detector without a weapon, the second door opens, the intruder takes the previously left weapon and enters the guarded room with it.

In automatic airlocks with semicircular doors from a number of manufacturers (SECOD, NUOVA VETRO, some models of SAIMA, TONALI), not only the floor is weighed, but the entire central part of the cabin, including the interior walls and ceiling. This allows you to detect objects left in the airlock, even if they are attached to the walls and ceiling.

Another method of detecting weapons left in the airlock is special radar systems used together with a floor weighing system, for example, in some SAIMA models.

The weighing system determines whether one or two people have entered the cabin by comparing the signal from the weight sensor with a threshold value. The value of this threshold value is set by the manufacturer or can be adjusted during commissioning of the cabin.

In automatic gateways of some manufacturers, for example SECOD, information from the weight sensor can also be output to the serial interface of an external computer. In this case, if the ACS database contains information about the weight of each person who has the right to access the protected facility, the weighing system not only ensures absolutely reliable control of passage “one by one”, but can be used as an additional identification system, practically eliminating unauthorized passage using someone else’s magnetic or proximity card.

The logic and algorithms of automatic vestibules are similar to those used in semi-automatic gateways. The difference is that the gateway logic of automatic cabins controls door drives rather than locks.

Automatic gateways are usually equipped with a built-in backup power source (batteries with a device for recharging them). In addition, it is possible to open the doors manually in an emergency.

Automatic cabins are usually equipped with a remote control panel, with which the security personnel of the protected facility can change the operating modes of the vestibule and control it manually.

The minimum set of functions implemented by the remote control panel:

• switching the airlock on/off

• switching on automatic or manual mode

• controlling doors in manual mode

• switching on emergency evacuation mode (simultaneous opening of two doors)

• switching on/off the metal detector

• switching on/off the “one at a time” passage system

In addition, the control panel usually displays information about failures in the main power supply network and the status of the backup power batteries.

Automatic gateways are integrated with the ACS in the same way as semi-automatic cabins.

The advantages of automatic vestibules include greater throughput compared to semi-automatic gateways and ease of use.

The disadvantage of automatic gateways is their higher cost compared to semi-automatic gateway cabins.

ROTANT revolving door cabins

Revolving door cabins are full-height electromechanical turnstiles, the blades and walls of which are made of bulletproof glass (bulletproof or resistant to penetration).

Revolving doors can have three or four blades, or two sectors (Fig. 8, Fig. 9, Fig. 10) Unlike conventional full-height turnstiles, metal detectors are built into revolving door cabins.

When a weapon is detected on a person passing by, the rotor of such a cabin switches to reverse rotation mode, forcing the intruder to exit the cabin.

However, with such an operating algorithm, the throughput capacity of the gateway is reduced and it is difficult for people to exit the protected premises.

This problem is solved by installing additional semicircular sliding doors at the exit from the cabin.

This solution is used, for example, in ROTOCOM cabins manufactured by SAIMA and PRIORA TONDA by TONALI. (Fig. 8)

When the metal detector is triggered, the direction of rotation of the rotor of these cabins does not change. Instead, the intruder's passage into the guarded premises is blocked by an additional door that closes only in front of the intruder. The exit from the premises remains open and the throughput capacity of the cabin does not decrease.

Additional sliding doors can be installed on one or both sides of the cabin. In this case, the described operating algorithm applies both when entering and exiting the protected premises.

Fig. 9. Cabin with a revolving door with four blades

Rice. 10. Cabin with a revolving door with two sectors

Like vestibule-airlocks , cabins with revolving doors can operate in manual and automatic modes, integrated with the access control system.

The main advantage of cabins with revolving doors is their very high throughput.

The disadvantages of these cabins are primarily their high cost is a major factor.

The areas of application of airlock cabins of various types are determined primarily by the requirements for throughput and cost constraints.

Cabins with revolving doors have the highest throughput and, at the same time, the highest price.

Semi-automatic vestibules, on the contrary, are characterized by low cost and low throughput.

Automatic gateways have average values ​​and allow the most reliable control of access to protected object.