Risk & Hazard Assessment

Fire risk assessment begins by separating two words that everyday speech muddles. A hazard is anything with the potential to cause harm - a source of ignition, a store of fuel, a route along which fire could spread. Risk is the combination of how likely that harm is and how severe it would be if it happened. A can of thinners is a hazard whether or not anyone is near it; the risk it poses depends on how likely it is to ignite and how many people its fire would threaten.

The distinction is practical, not pedantic, because it tells you what to do. You reduce risk by acting on either term: cut the likelihood (remove the ignition source, store the fuel safely, keep the two apart) or cut the consequence (fewer people exposed, faster escape, containment that limits how far a fire can reach). Often you do both. A crude but useful mental model is:

risk  ~  likelihood (how probable)  x  consequence (how bad)

> A hazard is the potential to harm. Risk is how likely that harm is, multiplied by how bad it would be. You design to shrink both.

Keep the two words apart in your own speech, too. When a client calls a material 'a fire risk', ask the real questions: how likely is it to ignite, and who would it harm - because the answer decides whether it is a trivial hazard to note or a serious risk to design against. This is why two buildings with identical hazards can carry very different risk: a fuel store beside a crowded dormitory is far higher risk than the same store in an isolated, empty shed, even though the hazard - the fuel - is the same. Risk assessment is the discipline of seeing not just what could burn, but who it would endanger and how badly.

With the language straight, the first real task is to find the hazards systematically rather than by hunch. A reliable way, rooted in the fire triangle of Module 1, is to hunt in three families.

Sources of ignition - anything that can start a fire: electrical faults and overloaded circuits, heating and cooking appliances, hot work such as welding and grinding, smoking, friction and hot surfaces in machinery, and deliberate ignition (arson, which serious assessments must consider). Sources of fuel - what will feed it: the building's contents and furnishings (today largely synthetic, fast-burning and producing toxic smoke), stored goods and packaging, flammable liquids and gases, waste and clutter, and combustible construction or finishes. Sources of oxygen are usually ambient, but note anything that adds to them, such as oxygen stores in healthcare, or ventilation that can feed a fire.

Then map the spread paths - the routes by which a small fire becomes a building fire: open doors and stairs, unsealed service penetrations, voids and false ceilings, combustible linings, and facades (Module 6). A hazard's danger is multiplied by how freely fire and smoke can travel from it to where people are.

HUNT IN THREE FAMILIES, THEN THE PATHS
  IGNITION  electrics, heat, hot work, smoking, friction, arson
  FUEL      contents, synthetics, stored goods, flammables, clutter, finishes
  PATHS     open stairs, penetrations, voids, combustible linings, facade

Housekeeping matters more than it sounds: a great deal of real-world fire risk is simply accumulated clutter meeting a careless ignition source on a route that should have been kept clear. Design can reduce the inherent hazards - separate ignition from fuel, specify less combustible materials, close off spread paths - but it must also make the safe state the easy state, so that good housekeeping is the path of least resistance rather than a constant battle. A bin store with nowhere safe to put the bins, or a plant room that doubles as the only convenient place to stack deliveries, is a design that quietly manufactures hazard no matter how diligent the occupants are. Give the fuel a safe home and the ignition sources a clear margin, and you have designed out risk that no amount of later vigilance could.

A fire risk assessment that stops at 'what could burn' is only half done. The other half - the half that makes it a life-safety exercise - is who could be harmed, and why they are especially vulnerable. The same fire is a minor event in one building and a tragedy in another because of the people in it.

Ask who is present and picture their disadvantages. People who are asleep (homes, hotels, hostels) lose the earliest, most precious minutes. People who cannot self-evacuate (hospital patients, care-home residents, the very young in a creche, people with disabilities) depend on others and on design - refuge, progressive horizontal evacuation, evacuation lifts (Modules 3 and 8). People unfamiliar with the building (visitors, customers, a congregation) do not know where the exits are and default to the way they came in. People in large numbers (assembly) must all move through limited exits at once, so small delays compound into crushes. People far from an exit, or below ground, or high up face longer, harder escapes. And lone or isolated workers may have no one to raise the alarm for them.

> Name the people before you judge the risk. The measure of a fire strategy is not the building it protects but the most vulnerable person inside it.

Vulnerability also shifts by time of day and by event: an office is low-risk at midday and higher at night, when a lone cleaner is the only occupant; a hall is transformed on the evening it is hired for a packed wedding. Assess the worst realistic combination of people and conditions, not the comfortable average. This is where occupancy classification (Lesson 2.1) and occupant load (Lesson 2.2) feed directly into risk: the class tells you the character of the people at risk, the load tells you how many. A serious assessment always designs for the least able occupant who could reasonably be present, not the fit adult who happens to be you.

Fire risk assessment is not a one-off document filed for approval; it is a repeating cycle that good practice runs through the life of a building, and that you, as a designer, should run in miniature at the drawing board. A widely used formulation - echoed in UK guidance and compatible with NBC-based practice - runs in five steps:

THE FIRE RISK ASSESSMENT LOOP
  1  IDENTIFY the fire hazards (ignition + fuel + spread paths)
  2  IDENTIFY the people at risk (and the most vulnerable)
  3  EVALUATE the risk, then REMOVE / REDUCE it (act on likelihood + consequence)
  4  RECORD the findings + the fire-safety plan; inform + train people
  5  REVIEW regularly + after any change of use, layout or occupancy

The loop closes on itself deliberately. Buildings change - a use drifts, a layout is altered, a store fills up, a tenant fits out a floor - and a risk assessment that was true at handover silently goes stale. The review step exists because the most dangerous assumption in fire safety is that yesterday's assessment still holds.

For a designer, steps 1 to 3 are a design-stage habit. As you place a boiler room, a kitchen, a store or a crowded hall, ask what could ignite, who it endangers, and how your plan cuts both - and let the answers reshape the layout before it hardens. Separate ignition from fuel, shorten the path from the riskiest rooms to an exit, contain the high-hazard spaces, and specify down the combustibility where people are most exposed.

But keep the honest boundary in clear view. A formal fire risk assessment for a completed, occupied or complex building is a specialist competence, often a statutory duty of the building's responsible person, and high-risk, crowded or unusual buildings need a fire engineer's judgement. Your job as a designer is to design out risk early, to make the safe state the easy state, and to know when the assessment exceeds your remit and belongs to an expert.