Modern warehouses come with added fire risk

Issue 7 2023 Fire & Safety, Transport (Industry)

With Africa’s transport and logistics sector returning to its rapid growth trajectory, the continent is seeing serious investment in modern warehousing. Naturally, there is a focus on protecting warehouses from theft, but fire is arguably an even greater danger. Modern warehouses are in themselves a valuable asset and fires threaten business continuity and have potential knock-on effects along supply chains.

A report by the World Economic Forum this year predicts that the African Continental Free Trade Area (AfCFTA) agreement, which introduces frictionless trade between its signatories, will be a catalyst for further rapid investment and expansion of the continent’s logistics sector. This new generation of modern African warehouses will be a promising economic foundation block for years to come.

In order to protect not just these substantial investments, but also the industries which they serve, Early Warning Fire Detection (EWFD) is essential. This is because once a fire has taken hold in a dense, high-racked modern warehouse, the chances of controlling it and preventing a total loss all but disappear.

Bigger warehouses, bigger risks

The experience elsewhere in the world shows that, as warehousing becomes more modern, the fire risks become larger. The trend is for warehouses to be bigger, with higher and more densely packed racks, and with greater levels of automation.

Newly constructed warehouse footprint sizes have been growing because logistics distribution operation has moved towards fewer but larger distribution centres. New-build warehouses are typically at least 25 000 m2 and can sometimes be more than 100 000 m2 in area. Additionally, goods can be routinely placed on racks 40 m high, or even higher where automatic storage and retrieval systems (AS-RS) are installed. As the level of warehousing automation increases, very high rack configurations and very narrow aisles become possible, thus further maximising total storage volume on the same footprint.

While these modern systems allow for more goods to be stored and moved, they are also a larger fire risk than smaller, conventional warehouses. Narrow isles and high racks mean fire will spread more easily, burn more fiercely, and be more dangerous to firefighters. Additionally, they mean that detectors and sprinkler systems situated at roof level, as is common in many smaller warehouses, will be less effective.

Huge potential loss

The vast quantities of goods stored in a large modern warehouse are only part of the increased risk when it comes to fire – albeit an important part – because once a warehouse fire is out of control, a total loss is likely. The automated systems and the warehouse structures themselves are also major assets that need to be protected. Naturally, they will be insured, but their sheer size raises further issues should a warehouse be lost overnight. Business continuity is paramount to deliver promised levels of service, and for high-value manufacturing processes to ensure just-in-time production and delivery.

The knock-on effects of a major blaze at a large modern warehouse are therefore many and severe. In many ways, regulations are yet to reflect the need to prevent such a scenario, or the challenges inherent in properly protecting such high, narrow racking of goods on a massive scale.

Since its first edition more than a century ago, the NFPA Fire Protection Handbook (currently in its 21st edition) always highlights the challenge and uniqueness of fire risks in warehouse and storage facilities. While warehousing technologies and material handling evolved over the years, many aspects of fire safety concerns, such as the potential for rapid growth of a fire and the dangers of manual fire-fighting in tight spaces amid racked goods, remain.

Early warning fire detection

Although sprinklers can prove effective in potentially reducing the fire damage and time to recover, they can also be destructive to anything from foodstuff to electronics. Only a well-designed Early Warning Fire Detection system, alongside staff trained in a fast response, provides real risk mitigation.

A suitable fire detection system is also required for the actuation of pre-action and co-incidence (or double interlocked) suppression systems. EWFD therefore goes hand-in-hand with an advanced sprinkler or other suppression system.

EWFD is based on the principle that a fire is far easier to put out if it can be detected in its incipient, smouldering phase. If staff on-site can be alerted to the fire at this stage, before flames are leaping into the air and spreading, they should easily be able to tackle it and the result will only be localised damage to a few affected goods. The challenge is, of course, that a tiny incipient fire gives off almost no heat and is therefore much harder to detect.

Aspirating smoke detection has the sensitivity

When it comes to the methods and devices required for EWFD in a large, tightly packed space such as a modern warehouse, aspirating smoke detection (ASD) is the only truly viable method. On the one hand, there is no reliance on heat, which can vary greatly in an African warehouse anyway. On the other hand, ASD has a level of sensitivity that standard, single smoke detectors cannot match.

In some settings, the ultra-high sensitivity of ASD can be a challenge in itself due to the possibility of triggering false alarms. However, a warehouse ought to be a smoke-free area. If even a small level is detected, it is worth investigating further. An advanced modern ASD system like SecuriSmoke has multiple levels of pre-alert exactly for this kind of situation; it is intended for a staged response where on-site security can investigate an area before launching a full-blown response involving suppression systems and an evacuation.

As well as its unrivalled sensitivity, ASD offers other distinct advantages in the modern warehouse environment.

ASD’s practical benefits in a warehouse

An aspirating smoke detector consists of a sensor and control unit incorporating a fan, and one or several tubes extending out to sample air across a large area. One immediate benefit of this is that testing and maintenance can be carried out at a convenient point at ground level. Because of the large volume of space that each unit can protect, there are also far fewer units to test compared to standard smoke detectors.

Testing and maintenance efficiencies are a major ROI advantage, but ASD also allows greater flexibility of design. Tubing arrays can be altered as necessary to fit new arrangements in the warehouse, and this is particularly useful when tubes are used vertically within racks in order to provide multi-level detection. Such vertical, in-rack sampling is critical for very high ceilings and when tight racking constrains the airflow, trapping smoke within the goods area. With other systems it becomes challenging to reach the units for testing, or to adjust systems when racks are rearranged.

Finally, ASD offers the reliability that key economic infrastructure deserves. There is no point in investing in state-of-the-art logistics if the chain cannot be relied upon, 365 days a year. The relatively small investment in EWFD, often offset by superior ROI over the long term, is therefore not just worth it, but essential.

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