What is protected space?

By Sam Gocher
Wednesday 7th September, 20223 minute to read

With pressurisation systems taking centre stage in the world of smoke ventilation in recent months, it’s important to continue understanding the different aspects and important elements of these systems. This is why it’s time to explain protected space.

What are protected spaces?

Protected spaces are relevant in all smoke ventilation systems, primarily in order to identify escape routes, however the focus on them only increases when it comes to pressurisation systems. This is due to a pressurisation system’s main purpose being to protect areas by increasing the air pressure in a protected zone relative to a fire zone.

What are the different types of protected space?

There are many different areas of a building which need to be protected. BS EN 12101-6, which is the British Standard for pressure differential systems, states: “Pressure differential systems offer the facility of maintaining tenable conditions in protected spaces, for example: escape routes, firefighting access routes, firefighting shafts, lobbies, staircases and other areas that require to be kept free of smoke.”

What is the definition of protected space?

In BS EN 12101-13, during the defining of pressure differential systems, page 5 of Part 13 states: “Pressure differential systems provide a means of maintaining tenable conditions in protected spaces, that are required to be kept free of smoke – e.g. escape routes, firefighting access routes, firefighting lift shafts, lobbies, staircases, and other spaces.”

While BS EN 12101-6 and BS EN 12101-13 offer different wording, both documents align on their definition of protected space.

How other documents define protected space.

In BS 9991, the current edition of this document doesn’t offer a direct definition of protected space, however in the ‘terms and definitions’ section of the document, protected spaces are mentioned throughout.

In BS 9991, the definition of a fire-fighting lobby is: “Protected lobby providing access from a fire-fighting stair to the accommodation area and to any associated fire-fighting lift.”

Fire-fighting shafts are defined as: “Protected enclosure containing a fire-fighting stair, fire-fighting lobbies, a fire main, and, if provided, a fire-fighting lift together with any machinery space.”

Fire-fighting stairs are referred to as: “Protected stairway communicating with the accommodation area only through a fire-fighting lobby.”

In the same section, BS 9991 also refers to protected spaces as corridors, lobbies, entrance halls and landings. There are however some changes on the way for BS 9991. If you’d like to find more out about these, we have a CPD dedicated entirely to this topic.

BS 9991’s sister document, BS 9999, defines the previously mentioned spaces in the same manner while also defining the word ‘protected’, as: “Enclosed (other than any part which is an external wall of a building) with fire-resisting construction.”

In BS 7346, part 8 of this standard doesn’t directly define protected spaces, whereas part 7, which is focussed on car parks, frequently refers toe protected space as ‘stairwells’. This occurs throughout sections such as Impulse Ventilation, and Smoke and Heat Control System Selection.

Finally, in the SCA Guide, section 5.2.1 states: “Most design guides identify the primary means of controlling the flow of smoke in residential buildings as the fire rated separation (i.e. the provision of protected escape routes and protected stairwells), with smoke control designed to supplement these provisions.”

In conclusion, it’s clear these documents all share a general understanding of protected space, with major definitions provided in BS EN 12101-6 and BS EN 12101-13.

There are some very helpful sources on our blog and YouTube where you can find out more information about pressurisation systems. We have videos: ‘What is a Pressurisation System?’, ‘What is the Stack Effect?’, ‘What is Protected Space?’ and ‘Pressurisation Systems - Air Release Explained’ which may be of interest. If you have any questions about pressurisation and/or protected space, please don’t hesitate to contact us.

What is Protected Space?

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