Tunnels and Metros

Independent Third Party Certification of Emergency Tunnel Ventilation Fans

Fan intended to ventilate underground space have a critical role to play in the event of a fire. The escape routes must be kept clear long enough for those trapped to escape, and consequently ventilation equipment must be able to clear hot gas and smoke for up to two hours in the event of a fire. The life-critical role of ventilation fans for underground spaces in the event of a fire is judged sufficiently great that within Europe third party independent testing is a legal requirement to verify that fans and there associated components do perform in accordance with the specification against which they are sold.

The European Commission (EC), the European Free Trade Association (EFTA) and the International Organisation for Standardisation (ISO) have addressed fire safety in emergency tunnel-ventilation systems. The EC and EFTA issued mandates for the creation of harmonised standards, and adherence to these standards demonstrates that industries are acting in compliance with European Union (EU) directives. Mandate M109 was issued to the European Committee for Standardisation (CEN) for the drafting of standards for “Fixed fire fighting systems” and Technical Committee CEN/TC 191 was formed for this purpose. Sub-Committee CEN/TC 191/SC1 is currently responsible for preparing and maintaining ten standards for Emergency Smoke and Heat Control Equipment. One of these EN 12101 standards, Harmonised Standard EN 12101-3, provides specifications against which accredited authorities must evaluate and certify powered emergency smoke and heat ventilators to comply with the requirements of the EU’s Construction Products Directive. Compliance with Harmonised Standard EN 12101-3 has, thus, become a legally enforceable requirement within EU member states.

The International Standards Organisation (ISO), a worldwide federation of national standards bodies, prepares international standards through various technical committees and their working groups. Each member body that is interested in an established technical committee subject has the right to be represented on that committee. Technical Committee ISO/TC 21/SC 11 formed for the purpose of preparing the International Standard ISO 21927 for emergency smoke and heat-control equipment, by agreement, closely follows the work of CEN/TC 191/SC1. To date, the standard consists of three parts:

• Part 1: Specifications for smoke barriers;
• Part 2: Specifications for natural smoke and heat exhaust ventilators; and
• Part 3: Specification for powered smoke and heat exhaust ventilators.

ISO 21927-3 is in accordance with the aims and objectives of the EC’s Harmonised Standard EN 12101-3; however, because ISO 21927-3 applies globally, it provides specifications against which appropriate authorities can evaluate and certify powered emergency smoke and heat control ventilators outside of EU member states.

ISO/TC 21/SC11 drafted ISO 21927-3 to provide a globally applicable means of specifying and approving powered smoke and heat control ventilators that: (i) facilitate the safe escape and/or rescue of people and animals in the event of a tunnel fire; (ii) protect property; and (iii) enable access to fight the fire whilst still in its early stages. ISO 21927-3 specifies the testing procedure for ensuring that fans and their motors conform to essential requirements.

Laboratories must perform sufficient tests to qualify a range of impeller diameters which may be scaled by factors of 0.63 and 1.26 from those tested. It is necessary to test:

• at least two fans at their highest rotational speed;
• the fan with the most highly stressed impeller;
• fans powered by motors with the smallest and largest frame sizes in the range at their highest outputs; and
• fans set up for testing in ways that represent the conditions to which they will be exposed in service.

The ongoing conformity of manufactured products with ISO 21927-3 must be assured by the application an audited factory production control (FPC) system. The standard recommends an FPC system that complies with ISO 9001:2000, but this must be made specific to the requirements of ISO 21927-3. A recent amendment further requires that a supplier’s conformity assessment declarations and documentation shall comply with ISO/IEC 17000, ISO/IEC 17050-1 and ISO/IEC 17050-2.