Information gathering is among the most fundamental of all human activities. Humans are immersed in a physical world that offers up a seemingly unending, and some might argue an ever increasing, stream of stimuli for our seeing, hearing, smelling, tasting and touching. We have developed highly sophisticated biological structures and cognitive processes for organising, managing and acting upon this onslaught of information. So seamless and elegant are these structures and process, that a great deal of what happens around us hardly gains our notice.

Fire engineers must ensure that building occupants become aware of potentially dangerous fire situations in time to take appropriate action. One way of doing this is by providing clear, consistent and easily recognisable cues. Consequently, fire engineers must have a sophisticated understanding of how people perceive fire-related stimuli.

Such stimuli include obvious signs of fire such as…

• Visible smoke or a smoke odour
• Radiant and convective heat from a proximate fire, or
• Arcing, sparks or visible flame. 
  

Of course, many of these cues pose the danger of physical harm. Exposure to excessive concentrations of carbon monoxide or other toxic compounds in smoke can cause hypoxia. High radiant or convective heat exposures can result in serious burns. However, these cues generally require little interpretation before individuals appreciate the danger present in a situation.

Less obvious signs of fire such as…

• Bells, horns or other audible warning signals,
• Loud indistinct or otherwise unrecognisable noises,�
• Flashing lights or a sudden flash of light,�
• A power outage or a sudden loss of telephone communication, or
• A sudden movement of other building occupants towards exits 
  

Require individuals to identify the source of the information or place it in some sort of situational context to appreciate its relevance. Information that appears incongruous or irrelevant will often provoke a human response, but this response may not be constructive in dangerous or threatening situations.

Among the most common ways of ensuring that people perceive fire danger in time to react properly is through the installation of mechanical or electrical systems to detect fire signatures and translate them into signals that will be interpreted as a fire warning. Fire detection and alarm systems can expedite the detection of fire cues and shorten the time between detection and response by translating early fire cues into a warning. Under ideal conditions, such systems can also provide an indication of the location, intensity and nature of the fire threat or suggest an appropriate response. However, proper interpretation and action on fire warning signals or instructions requires training. People can be conditioned to disregard signals through frequent exposure to false or nuisance alarms.

Fire warning systems in New Zealand currently employ a number of different types of signals and signal patterns to alert building occupants to a potential fire so they can evacuate. This remains true despite the fact that an international standard for fire evacuation signals — ISO 8201 — has existed since 1982. This signal consists of three half-second tonal elements separate by half-second intervals. Each group of three tones, is separate from the next by a 1.5 second interval. This signal is often referred to as the temporal Code 3 pattern, and can be produced by a wide variety of fire warning devices, including bells, vibrating horns, sirens, tone generators and single-stroke chimes.

The New Zealand Fire Service often recommends the installation of smoke alarms and fire detection and alarm systems to provide early warning of fire danger. We encourage building owners to select and install fire warning devices that emit a uniform fire warning signal and to train building occupants to recognise this signal and practice their response.