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Carrying on with the theme of Smoke Extraction from last year, this month we will look at a slightly different product, a Natural Smoke and Heat Exhaust Ventilator (NSHEV).
A natural smoke and heat exhaust ventilator (NSHEV) is a passive ventilation product designed to automatically open (this can be manually operated in certain instances) in the event of a fire to allow, through the process of natural ventilation, external exhausting of heat and toxic gases from buildings helping to prevent the spread of fire and improve visibility for occupants and firefighting personnel.
The current European standard for NSHEVs is EN12101-2:2003. A later version of the standard (2017) was produced; however, as it was never published in the Official Journal of the European Union (OJEU) it is not current under the Constructions Product Regulation (CPR), and you can only CE / UK CA / UK NI mark against the 2003 version. The 2017 version of the standard gives more details in the sections on requirements, Assessment and Verification of Constancy of Performance (AVCP), and the Annex’s on testing. Swegon recommend designing and testing to the 2017 version (wherever possible) and certifying to the 2003 version.
Both the 2003 and 2017 version of the standard are different to the standards that I have discussed in other blogs, as the document incorporates the product, test and classification into one document. There is no Extended Field of Application document for NSHEV’s. The test methods to evaluate the performance of the product are:
- Annex B: Aerodynamic free area
- Annex C: Reliability
- Annex D: Opening Under Load
- Annex E: Low Ambient Temperature
- Annex F: Wind Load
- Annex G: Heat Exposure
- Reaction to fire classification
It is possible to achieve certification without meeting all the annexes listed above. The declared product classification will define what has been tested, and you (the designer) must decide if it is appropriate for the application.
However, be vigilant!
A product that is promoted as an NSHEV but has no declared performance against heat exposure, would not be considered appropriate for any NSHEV application.
The following factors should be considered when selecting/reviewing an NSHEV product:
Heat Exposure
NSHEVs are normally referred to as Automatic Opening Vents (AOV); however, a damper installed in a wall of a corridor for the purposes of Smoke Extraction (sometimes called a corridor damper) may also be referred to as an AOV. It is vital to understand the difference between the two.
Within a building, a Smoke Shaft will usually be considered a fire compartment. Any product installed within the compartment lining needs to have the appropriate test data to show that it will maintain compartmentation in the event of a fire if it is not required to extract smoke. This test evidence would be a Fire resistance test as specified in EN1366-10 (which refers back to EN1366-2) in an appropriate supporting construction for the application.
The test in Annex G is a Heat Exposure test, not a Fire resistance test. It is conducted at either 300C or 600C. The test temperature is decided by the test sponsor, but for products with aluminium frames, the temperature would be 300C due to the melting point of aluminium. For this reason, an NSHEV must never be used in an application where compartmentation is required, such as being fitted into a Smoke Shaft.
Reliability
The Annex C reliability test is designed to simulate the vent going to its fire-open position. The standard allows several classifications, and as mentioned before, you need to consider what is appropriate for the application.
If the NSHEV is also intended to be used as a dual-purpose ventilator, i.e. day to day ventilation, it needs to be tested for 10,000 cycles in addition to the Annex C requirements.
BS9999:2017 section I.3.5, Smoke Control Systems for Means of Escape, gives details on the frequency of testing. If you are Designing or undertaking product selection, you need to make sure that the classification of the product you have selected meets your cycle requirements.
Actuator
The standard requires you to test both the ventilator and actuator together. You cannot test a ventilator and apply any actuator to it. Likewise, you cannot test an actuator and apply it to any Window. The NSHEVs are tested as an assembly.
Declaration of Performance
The manufacturer of NSHEV units is required to supply a Declaration of Performance for the product. As defined in EN12101-2:2003, this must include:
- Name and address of the manufacturer or his authorised representative established in the EEA and the place of production.
- Description of the product (type, identification, use) and a copy of the information accompanying the CE/UK CA/ UK NI marking.
- Provisions to which the product conforms (i.e. annexe ZA of this EN);
- Particular conditions applicable to the use of the product [if necessary].
- Name and address (or identification number) of the approved body (bodies).
- Name of, and position held by, the person entitled to sign the declaration on behalf of the manufacturer or his authorised representative.
For characteristics where certification is required (system 1), the declaration shall contain a certificate of conformity with in addition to the information above, the following information:
- The name and address of the certification body (this is a third party certification body)
- The certificate number.
- Conditions and period of validity of the certificate, where applicable.
- Name of, and position held by, the person entitled to sign the certificate.
So, to summarise NSHEVs lack known Fire Resistance and are solely tested against heat exposure making them unsuitable for compartmentation. It is also important to clarify the chosen NSHEV has the necessary declared product classification for its application. For example, if it is being used for general ventilation purposes, it needs to have also done the additional 10,000 cycle test. Furthermore, it is vital to note that the actuator and ventilator are tested together.
