BMS Alarms and security

BMS Alarms and security

All modern building automation systems have alarm capabilities. It does little good to detect a potentially hazardous or costly situation if no one who can solve the problem is notified. Notification can be through a computer (email or text message), pager, cellular phone voice call, audible alarm, or all of these. For insurance and liability purposes all systems keep logs of who was notified, when and how.
Alarms may immediately notify someone or only notify when alarms build to some threshold of seriousness or urgency. At sites with several buildings, momentary power failures can cause hundreds or thousands of alarms from equipment that has shut down – these should be suppressed and recognized as symptoms of a larger failure. Some sites are programmed so that critical alarms are automatically re-sent at varying intervals. For example, a repeating critical alarm (of an uninterruptible power supply in 'bypass') might resound at 10 minutes, 30 minutes, and every 2 to 4 hours thereafter until the alarms are resolved.
  • Common temperature alarms are: space, supply air, chilled water supply, hot water supply.
  • Pressure, humidity, biological and chemical sensors can determine if ventilation systems have failed mechanically or become infected with contaminants that affect human health.
  • Differential pressure switches can be placed on a filter to determine if it is dirty or otherwise not performing.
  • Status alarms are common. If a mechanical device like a pump is requested to start, and the status input indicates it is off, this can indicate a mechanical failure. Or, worse, an electrical fault that could represent a fire or shock hazard.
  • Some valve actuators have end switches to indicate if the valve has opened or not.
  • Carbon monoxide and carbon dioxide sensors can tell if concentration of these in the air is too high, either due to fire or ventilation problems in garages or near roads.
  • Refrigerant sensors can be used to indicate a possible refrigerant leak.
  • Current sensors can be used to detect low current conditions caused by slipping fan belts, clogging strainers at pumps, or other problems.
Security systems can be interlocked to a building automation system. If occupancy sensors are present, they can also be used as burglar alarms. Because security systems are often deliberately sabotaged, at least some detectors or cameras should have battery backup and wireless connectivity and the ability to trigger alarms when disconnected. Modern systems typically use power-over-Ethernet (which can operate a pan-tilt-zoom camera and other devices up to 30–90 watts) which is capable of charging such batteries and keeps wireless networks free for genuinely wireless applications, such as backup communication in outage.
Fire alarm panels and their related smoke alarm systems are usually hard-wired to override building automation. For example: if the smoke alarm is activated, all the outside air dampers close to prevent air coming into the building, and an exhaust system can isolate the blaze. Similarly, electrical fault detection systems can turn entire circuits off, regardless of the number of alarms this triggers or persons this distresses. Fossil fuel combustion devices also tend to have their own over-rides, such as natural gas feed lines that turn off when slow pressure drops are detected (indicating a leak), or when excess methane is detected in the building's air supply.
Good BMS are aware of these overrides and recognize complex failure conditions. They do not send excessive alerts, nor do they waste precious backup power on trying to turn back on devices that these safety over-rides have turned off. A poor BMS, almost by definition, sends out one alarm for every alert, and does not recognize any manual, fire or electric or fuel safety override. Accordingly, good BMS are often built on safety and fire systems.

BMS Information security

With the growing spectrum of capabilities and their connection with the Internet, building automation systems were repeatedly reported to be vulnerable, allowing hackers and cybercriminals to attack their components. Buildings can be exploited by hackers to measure or change their environment: sensors allow surveillance while actuators allow performing actions in buildings (e.g. opening doors or windows for intruders). Several vendors and committees started to improve the security features in their products and standards, including KNX, ZigBee and BACnet. 


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