Smoke Pressurisation Systems are designed specifically for Life Safety and Asset Protection, and their Whole Life Support Management must take into account the importance of maintaining the correct performance levels throughout their Design Life.

They differ from all other types of active smoke control in that Pressurisation Systems rely heavily on the integrity of the building structure to continue to perform as designed.

For this reason, the Standards and Regulations developed for their maintenance require a rigorous and frequent comparison performance examination of all elements of the scheme.

What do they do?

All Pressurisation Systems are designed for 'Means of Escape', 'Fire Fighting Access', or both.
They provide two main functions

- Positive air pressure within circulation (escape) areas

- Controlled air flow through accommodation areas

Are all systems the same?

The British Standard (BS5588:1998 Part 4) recognises 5 Classifications of buildings where Pressure Differential (Smoke Pressurisation) Systems are used. The selection depends on the type of building, nature of occupancy, building use and a wide range of other considerations.

Ultimately, each system is designed for a specific application and no two systems are the same.

What are the components?

Unlike other types of active smoke control, Pressurisation Systems can be difficult to recognise. They generally comprise:

- Duty/standby fan sets (normally mounted at or near roof level).

- Ductwork from the fan sets to the pressurised areas, with volume control dampers and outlet grilles at carefully selected locations.

- Pressure relief dampers and egress air fans/ventilators where appropriate.

- Alarm linked control equipment (with supported power supply), including Fireman's controls.

Physically, they can appear to form (and are often mistakenly maintained as) part of the general HVAC package, and only closer examination of the system and Fire Strategy Documentation can reveal their true function. Grilles in lobby, corridor, or stairwell areas are often the main clue to their existence.

Why is pressurisation so important?

The most common cause of death in fires is from asphyxiation. Pressurisation Systems provide and maintain a positive supply of uncontaminated air into the escape routes, preventing smoke ingress and providing a clear, uncontaminated escape route.

For designated 'Fire Fighting Access' systems, there is an additional Duty of Care as Pressurisation Systems not only provide safe environment areas to allow the Fire Brigade to safely enter a Building during an active fire, but also a safe, direct route to the source of the fire.

Why are systems affected by building changes?

The pressure levels/egress velocities achieved on a system are critical to its overall performance.

Too little pressure and the area could be overwhelmed (smoke ingress); too much and escape doors may become 'locked' with over pressure.

In either case, the result could be potentially disastrous. One wedged open door or failed door closer for example, can defeat a complete Pressurisation System.

Why comparison test?

Part of the rigorous service cycle requires mandatory regular comparison testing of the scheme against original commissioning data.

This provides confirmation that the pressure/velocity levels are retained within the guidelines.

Even small changes to the pressurised area can seriously affect overall performance, for example:

- Changes to the building structure

- Weakened automatic door closers

- Worn or dropped hinges

- General door damage creating excess leakage paths.

A visual inspection is insufficient to determine the overall effectiveness of the pressure system - only performance comparison testing will highlight defects.

What support is required?

Regulatory Compliance and Certification of active Pressurisation and Pressure Differential Systems requires specific expertise and levels of whole life support.

It is not sufficient to maintain these schemes as part of the HVAC package, since different and quite specific Regulations and Standards apply, in keeping with their accepted importance as Life Safety Systems.

Where original Commissioning information is not available, then it is necessary to carry out a detailed design review to determine the nature and required performance criteria for the installed system prior to carrying out servicing and comparison performance tests.

Airvent offer a nationally supported base of expertise to commission, re-commission, service and performance test all types of Pressurisation Systems to ensure Regulatory Compliance.