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In this Fire Safety Technical Note we outline the three potential solutions to preventing water ingress to firefighters lifts in accordance with BS 9999.

What is a Firefighters Lift?

A firefighters lift is a specifically designed lift installation that is intended to operate as long as practicable when there is a fire in parts of the building beyond the confines of the firefighting shaft. The lift itself is used as part of a firefighting intervention strategy to transport firefighters and their equipment throughout the building when undertaking firefighting operations.

A firefighters lift installation includes the lift car itself, the lift well and the lift machinery space, together with the lift control system and the fire and rescue service communications system.

What is the Hazard Associated with Water Ingress?

Water resulting from either automatic fire suppression systems or from firefighting operations may be present within the firefighting lobby during a fire. As a firefighting lift is designed to continue operation during a fire event, there is a risk that this water ingress may enter the lift installation and impair its use. 

For example, any water entering the lift well or the lift car itself can cause the installation to malfunction and undermine the firefighting intervention strategy resulting in loss of communications or entrapment of firefighters.

What is BS 9999?

BS 9999:2017 is a British Standard that provides practical guidance on meeting the functional requirements of the Building Regulations. BS 9999 provides more technical guidance than Approved Document B, however serves a similar function in that it acts as a standalone design document that can be used to develop the fire strategy for a building.

The guidance of BS 9999 is predicated on a risk-based approach as opposed to the prescriptive approach of Approved Document B and is therefore commonly used in more complex buildings that are beyond the scope of the Approved Document. Neither Approved Document B nor BS 9999 are mandatory, and designers can use the guidance of either document in developing fire strategy solutions for a building.

What Does BS 9999 Say about Water Protection of Lift Wells?

Section 20 of BS 9999 provides guidance on Facilities for Firefighting with clause 20.4.5 specifically addressing the hazard of water ingress into firefighters lifts. Annex N of BS 9999 provides three typical arrangements for preventing water ingress into a firefighting lift installation.

What are the Three Potential Solutions for Preventing Water Ingress?

The first solution is to provide a raised threshold at the lift entrance. 

BS 9999 recommends this threshold be at least 25mm in height and be provided at the threshold of the lift landing door at each floor level. The intent of this arrangement is to allow for water to pool in the lift landing however prevent ingress into the lift car or shaft.

The second arrangement is to provide a drainage grid. 

The drainage grid should be positioned adjacent the landing door with a raised threshold where the lift door is accessed, with the drainage grid leading to a gulley which in turn leads to a drainpipe. The intent of the drainage grid solution is to provide a run-off for water to prevent pooling in the lift lobby.

The third arrangement is to provide a sloped floor within the lift lobby. 

In accordance with BS 9999 this floor should slope away from the lift installation with a minimum fall of 1:100. The highest part of the floor (adjacent the lift lobby) should be at least 25mm higher than the lowest part of the slope. The location of other features within the lobby should be considered, for example any rising main that may contain water. The intent of a sloped floor in this situation is to ensure that any water present in the lobby pools away from the lift installation and that any water ingress is limited.

Are There Other Considerations for Firefighters Lifts?

A firefighters lift is a critical element of a firefighting intervention strategy and should be carefully designed to ensure its effectiveness as well as the safety of those entering the building during a fire event. In addition to water ingress other considerations include the position of the lift with respect to the firefighting stair, the size of the firefighting lobby and the provision of suitable ventilation.

Specialist advice can be obtained for new and existing lift installations from the project fire engineer or from a VT (vertical transportation) consultant.