Pressurisation fans for Nottingham’s Crowne Plaza
Pressurisation smoke control systems are designed to keep hot smoke away from escape routes in multi-storey buildings, using mechanical intervention in the form of fans mounted on the roof of the building. The idea is to use pressurisation fans to create an air pressure barrier, stopping hazardous smoke from spreading into stairwells but not over-pressurising to the point where it becomes difficult for escaping people to open doors etc.
In the case of the nine storey Crowne Plaza Hotel, Nottingham, a series of Brakel Airvent performance comparison tests had identified flaws in the pressurisation system, with adequate airflow figures not being met when the pressurisation fans were running at the head of the three stair cores in the building. It is a legal requirement – under the Regulatory Reform (Fire Safety) Order 2005 – that smoke control systems be properly maintained and continue to operate in accordance with the original design intent and recommended guidelines.
The airflow criteria are based on maintaining a velocity through the doorway between the pressurised space and the accommodation on the fire floor of not less than 0.75m/s.
The pressure criteria are based on maintaining the following pressures:
- 10Pa when all doors inside the pressurised space are open
- 10Pa when a door on another floor (unaffected by the fire) is open
- 50Pa when all the doors inside the pressurised space are closed
To solve the problem, Brakel Airvent recommended a refurbishment of the system, particularly the replacement of the three fan arrangements with upgraded versions. New roof-mounted duty/standby fans will be installed, along with inverter drives allowing for soft start and variable speed control. The fans will be connected to the head of each stairwell via three sets of bespoke galvanized ductwork assemblies. All works will be undertaken with due care and consideration given to the inherent risks of rooftop working at height and working within a live hotel environment.
In addition, new pressure sensors and fireman’s override switches will be installed and connected to a new control panel in the 8th floor plant room.
The updated system will result in correct pressurisation and airflow rates within all three stairwells, ensuring clear routes of escape in the event of an emergency active fire situation.