The recent Cyclone Debbie disaster and its aftermath in Queensland and New South Wales' Tweed Coast and Northern Rivers was one of the most catastrophic weather events on record.

It left behind more than half a billion dollars in damage and untold human tragedy, including the loss of lives, loss of life-long possessions such as homes and property, loss of businesses, of livelihoods and income.

It reminds all of us that regardless of where we live in this great country, nature can have a profound impact of our safety and well-being.

Fire protection systems can be a seriously impaired by floodwater inundation, a fact that is sometimes overlooked when considering the range of other traumatic impacts caused by these types of weather events.

A great deal of useful information is available on the potential for impairment of active fire protection systems and equipment as a result of inundation. The potential for immediate damage or subsequent deterioration of things like fire pumps, smoke detectors and electrical control panels is both reasonably obvious to most and is generally pretty easy to demonstrate or test for – at least in the short term.

Perhaps a less obvious and certainly far harder to detect and demonstrate consequence of inundation is the effect on passive fire elements – particularly fire doors.

In the case of fire walls, structural walls are invariably of brick, concrete or other masonry. Most people would agree that once cleaned and dried, such elements are likely to perform as required. Lightweight partitions with a fire resistance level (FRL) are generally constructed of paper clad gypsum board and invariably will disintegrate or deteriorate in an obvious manner and require replacement after a flood. The damage to fire doors is less obvious.

There are a number of different manufacturers of fire doors and a number of different ways by which the door achieves its required FRL. Typically, the vast majority of door panels consist of a wooden peripheral frame comprising two vertical stiles, two horizontal rails; a fire-resistant core of either vermiculite, calcium silicate, cellulose fibre or mineral fibre; and facing panels on either side of the door leaf of plywood, mdf or metal sheet.

Whilst there are rigorous test criteria with which fire doors must be shown to comply to validate their approvals – including tests for misuse, slamming, body impact and of course fire resistance – none of the criteria (or tests) relate to water resistance. It is therefore the case that fire doors typically only have the level of water resistance anticipated for an ‘ordinary’ door in order to meet common law/trade practices requirements to be fit for purpose.

Indeed, since by definition the vast majority of fire doors are internal doors (as they separate adjacent fire compartments) it is not necessarily safe to assume that they have any significant level of weather resistance, let alone resistance to immersion in water.

The layers of fire resistant compound packed in the cores of fire doors, along with the joins in the critical wooden framing required to hold those cores in place can and will be damaged by water immersion. In some cases, the core may be considered to be like a Weet-Bix that will essentially disintegrate and fall to the bottom of the door after becoming waterlogged. Even if all that happens is that the wood swells and deforms and the door’s tolerances change, or that its internal structure is contaminated with the unknown contents of the floodwater, it can no longer be relied upon to function as required in a fire.

Of course, that is the critical point: it is only when the door is actually subjected to a fire that we will know whether it still works, and it is then too late to find out. Once a door has been even partially submerged, we know it has been subjected to a condition for which it was not designed and we know what the adverse effects of that immersion could be. Such doors would require destruction to validate any internal damage and so must be replaced.

As an industry, we carry out routine service of fire doors for clients. Naturally, the doors in question constitute prescribed fire safety installation/s and our advice to the occupant/occupant’s representative will be that flood subjected doors need to be replaced rather than allowed to remain in that compromised state.

Years ago, the space shuttle Columbia disintegrated spectacularly over Texas because of the failure of its heat resisting shield. It failed because it was subjected to a condition for which it was not designed – namely the impact of foam insulation shed from the external tank during launch.

With regard to flooded doors, they too have been subjected to a condition outside those for which they were designed – namely submersion, not just in water but in a noxious soup of contaminants ranging from suspended solids, to solvents to sewerage. It should call into question their ability to now do the job for which they were designed and installed – to contain a fire. Unlike the Challenger, however, the fix is simple, obvious and relatively inexpensive.