NOTE General recommendations applying to all building types are given in

Section 4 to Section 9. This annex gives additional recommendations that are specific to process plant and outdoor structures. Such buildings need to meet both the general recommendations in Section 4 to Section 9 (where applicable; see the Commentary below), and the specific recommendations given in this annex.

COMMENTARY ON ANNEX F

a) General recommendations of the British Standard apply to all buildings, but may not be suitable for buildings designed for process and storage plants.

b) Such buildings may be fully enclosed or open structures with minimal internal divisions and low occupancy (typically fewer than ten people).

c) Design considerations for these buildings are general and specific recommendations might be inappropriate or restrictive.

d) Relevant regulations include:

· Regulatory Reform (Fire Safety) Order 2005

· Fire (Scotland) Act 2005

· Fire Safety (Scotland) Regulations 2006

· Fire Safety Regulations (Northern Ireland) 2010

F.1 General

For process plants and outdoor structures where full recommendations for means of escape and structural design are impractical:

a) Consult relevant authorities early in the design process.

b) Consider the overall fire safety measures, including:

· Automatic fire detection

· Extinguishing and smoke control systems

· Localized suppression systems

F.2 Process plant buildings

a) Design Considerations for Process Plant Buildings:

a) Ceiling Heights and Openings: Higher ceilings and numerous openings increase early fire awareness by individuals, independent of alarms.

b) Smoke and Fire Threat: Rapid fire escalation and thermal radiation are key concerns. While travel distances remain applicable, some flexibility in escape route widths and vertical means of escape may be acceptable.

c) Escape Arrangements: Buildings with reduced smoke threat and low occupancy may have:

· A single protected or external escape stair

· Alternative means of escape, such as internal/external stairs or ladders

d) General Rule: For other process plant buildings, follow the standard recommendations for means of escape.

F.3 Weather housed plant buildings

NOTE The purpose of these buildings is solely to provide enclosure of the process plant to control the environment for operator comfort and/or to protect the plant from the effects of the weather. They are typically large hangar or shed-like buildings, often without discernible floors, but rather galleries, walkways and connecting stairs associated with the process plant itself.

The following factors should be taken into account when designing weather housed plant buildings.

a) Escape Route Considerations for Process Plant Buildings:

a) Travel Distances & Vertical Components:

· Increased travel distances and unenclosed vertical escapes may be allowed if sufficient escape routes remain effective early in a fire.

· External escape routes can be used if they have adequate protection against smoke and heat, and egress to safety is clear.

b) Alternative Routes:

· Alternative routes should be separated by at least 90° horizontally and 20 m vertically, or be at opposite ends of the structure, unless otherwise separated for fire resistance.

c) Travel Distances:

· Travel distances should align with Table F.1.

· If exact distances are unknown, use two-thirds of the direct distance as a reference.

Table F.1 Maximum travel distances for weather housed plant buildings, weather protected plant and external plant.

F.4 Weather protected plant

NOTE These buildings serve a similar function to that for weather housed plant (F.3), but are distinguished from these by large areas of openings that breach the enclosure. These can be for process reasons, including ventilation; e.g. ridge vents at high level, and louvres or open sides at low level. As a consequence, the potential for smoke logging is mitigated.

Where the hazard from fire on weather protected plant is determined to be akin to that for external plant (F.5), the travel distances for external plant given in Table F.1 should be used.

F.5 External plant

The following factors should be taken into account for external plant.

a) Escape Routes for External Plant:

· Number & Separation:

· Provide at least two escape routes from any part of the plant, positioned as clear alternatives to avoid being affected by the same fire.

· Horizontal routes should be at least 90° apart, and vertical routes should be a minimum of 20 m apart or at opposite ends of the structure.

· Travel Distance:

· Measure travel distances to a safe point outside the plant (e.g., access roadway, open ground) that ensures unrestricted egress to a safe assembly point.

· Escape routes do not always need to descend directly to ground level; walking away from the fire at high levels may be safer.

· Dead Ends:

· Tall, isolated plant units (e.g., distillation columns) may be dead ends. Risk reduction measures (e.g., remote monitoring) should be implemented as alternatives to requiring multiple escape routes.

· Classification & Travel Distances:

· Normal Fire Hazard Zones: Includes tank farms, silos, pipe-rack areas. Follow Table F.1 for travel distances.

· High Fire Hazard Zones: Units with extremely high fire danger (e.g., flammable liquids or gases). If equipped with a sprinkler system, follow Table F.1 for travel distances.

NOTE 1 Risk profile A4 is unacceptable within the scope of BS 9999 (see Table 4). If a sprinkler system or another appropriate fire suppression system is installed, the risk profile is reduced to A3 (see 6.5) and the travel distances in Table F.1 apply. If such a system is not installed, a fire engineering solution would be required which is outside the scope of BS 9999.

NOTE 2 The processing of toxic materials does not lead to “high fire hazard outdoor zone” status unless their substantial release is probable in the early stages of a fire, or the material itself is flammable or flammable materials are involved in the process in a manner to present an extremely high fire danger.

Account should also be taken of the occupancy levels and their duration.

NOTE 3 Although units of external plant are typically very large, the number of personnel operating them is usually small, where parts might only be periodically visited. Therefore, in determining adequate means of escape in high hazard outdoor zones, two frequencies of visit are distinguished, i.e. “frequently visited” and “not frequently visited”. “Frequently visited” means:

a) visited once a day or more;

b) visited once a week or more by a group of three or more persons; or

c) visited for the purposes of taking samples of flammable gas or liquid at a temperature above its flash point.

Annex F (normative) Process plant and outdoor structures