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VESDA smoke detection verse Standard point detection in data centres and server rooms.
Traditional Point Detection
Point detection has traditionally been used for smoke detection with data centres and server rooms. Point detectors are reliant on enough smoke contamination over its chamber to initiate and alarm.
Historically a mix of both Ionisation and optical detectors were used for fire suppression systems for server rooms. This would provide a greater bandwidth for different densities of smoke.
Ionisation detectors were always sensitive to high airflow, so the spacing of the detectors was critical, so not have the ionisation smoke detectors close to air handling units.
These days most optical smoke detectors are sensitive enough to cover most eventualities within data centres/server rooms.
The problem still exist, that we ideally need still air to accurately detect smoke.This means shutting down air-conditioning equipment when the first detector is activated, which is NOT an ideal solution for the newer high heat generating server racks.
VESDA smoke detection
With the introduction of laser based smoke detection technology, we now have an alternative to the limited scope of the traditional point detector.
VESDA aspirating smoke detection systems provide phenomenal response to smoke within high airflow environments. In fact, VESDA is so good that it can detect incipient stages of combustion with the air sampling pipes placed over the return air grills of the air handing equipment.
This makes good sense for any server room/datacentre, as this is the first place that smoke will travel.
Secondary smoke detection is also used for the eventuality that the Air handling equipment fails or is switched off.
VESDA systems are designed using the same principles as point detection. The same industry design standard (BS6266 - 2008) applies.
Additional standards are also applied such as the EN54-20 for enhanced smoke detection (something that is not available via standard point detectors).
Using the Xtralis's VSC programming and reporting software, VESDA smoke detectors can be calibrated to any desired activation smoke threshold.
In addition to this, there is a minimum of three levels of smoke threshold that can be programmed. These are:-
With these additional smoke thresholds (which are not available with point detectors), versatility can be programmed to prevent unwanted discharges, or more importantly keeping incipient fire incipient by providing very early warning to any smoke detected.
Hot wire test
There are a number of tests that can be used to commission a VESDA system. For data centres a hot wire test is best. This test is based on 1 metre of test wire with a high electric load passing through it. As the wire heats and the insulation melts the VESDA detector will respond.
Smoke Threshold calibration
VESDA smoke detectors are capable of
collating up to 18000 events, including smoke changes. The VSC software will generate a smoke trend graph which will allow visual programming of the smoke threshold levels. This facility allows users and engineers to agree appropriate activation points for Alert, Action and Fire outputs.
Quaterly, bi-annual routine maintenance is also assisted with the event log that VESDA provides. Ambient dust levels can be monitored and thresholds adjust if required. All server rooms and data centres will collect dust over time. VESDA will report higher dust levels, so that will provide additional protection against unwanted fire suppression system discharges.
Post discharges - Gas released
With the reporting facilities of the VSC software, any discharge that occurs, VESDA will provide a detailed breakdown of events leading up to the discharge. All these events are date and time stamped so that the source of ignition can be better identified.
Unlike conventional point detectors which only provide 'head removal' fault reporting, VESDA will provide a full breakdown of faults present. These include:-
Power Supply faults
Air sampling pipes are connected to the VESDA smoke detectors. These pipes are installed within floor, room and ceiling voids and allow smoke to pass via the sampling holes to the VESDA smoke detectors.
This means that the fire alarm engineer does not need to disturb the fabric of the room, as all the fault finding can be done via the VESDA smoke detector located at a convenient height and location within the room.
Fault finding is also made easier with the advanced and detailed reporting capabilities of the VSC software.
Room Extensions or alterations
When the IT equipment out grows the server/data room, the room may be extended to provide extra space for additional IT hardware, or, it may also be that the computer room is being reduced in size to accommodate that newest micro technology. The versatility of a VESDA smoke detection system, is that the air sampling pipes can be easily adjusted to accommodate a change and the VESDA simply re-normalised and commissioned.
In addition to all the benefits above, VESDA systems can be performance tested before they are installed using Xtralis's Aspire design software. This ensures that optimum performance can be design before installation and then measured and verified during commissioning.
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