Principal contractors have management and control of construction sites and therefore have the primary obligation to ensure lighting is sufficient for workers to safely evacuate in emergencies and permit emergency or repair personnel to access the site. Unlike finished buildings, evacuation routes on construction sites often contain construction materials, electrical switchboards, portable equipment and other obstacles.
On sites where natural lighting is insufficient, evacuation lighting is normally provided by installing battery powered emergency lighting and exit signs. AS/NZS3012 Electrical installations on construction sites and demolition sites, clause 2.7.3, sets out that a minimum light level of 20 lx be provided for a minimum of one hour following the loss of normal lighting.
This minimum level applies to the site’s designated evacuation routes. Emergency lighting should also be installed at or next to site switchboards to help restore normal lighting after a fault occurs.
Note: the 20 lx is an average light reading and can be determined using the advice given below.
Worker evacuation must be considered in the project’s planning phase. The principal contractor should make electrical contractors aware of the project’s evacuation lighting requirements during the construction wiring tender process. These requirements should take into account that evacuation lighting may need to be relocated at various construction phases.
As part of the site’s emergency response plan the principal contractor should designate evacuation routes for the various work areas. The routes should be regularly reviewed over the life of the project to ensure they remain effective as the site layout changes.
In multi-storey buildings any active stairway will be used by personnel during an emergency, so each active stairway should be treated as an evacuation route.
When evacuation lighting is required
Site evacuation routes require evacuation lighting where:
• work is outside full daylight hours (evacuation lighting may need to be installed as the year progresses and days shorten), or
• natural lighting does not maintain the minimum lighting level being 20 lx (eg basements, internal passageways or shading from near by buildings).
Note: If any work area, including under temporary support structures (eg formwork decks), is not sufficiently lit by the evacuation route lighting additional emergency lighting should be installed to light the work area to allow safe exit.
Exits signs must not be positioned more than one metre above or two metres in front of the exit. If the evacuation route turns, or does not lead directly to an emergency exit, then exit direction arrow signs that point towards the emergency exit must be installed at each change of direction.
Exit signs, including exit directional arrow signs, should be the internally illuminated battery back-up type so they are visible through smoke. In specific circumstances, however, clause 6.3 of AS/NZS 2293 Emergency escape lighting and exit signs for buildings, states that externally illuminated signs may be suitable. This is only in areas that have appropriate means for automatically exhausting or excluding smoke. Exposure to open air does not meet this requirement. Externally illuminated signs, where permitted, must be directly illuminated by an emergency light.
Reusing evacuation light fittings
Often, evacuation light fittings are reused from previous sites or other temporary installations (eg from completed lower floors of a multi-storey site). As the lamps and batteries age, the drop in light output must be managed to ensure minimum evacuation lighting levels are maintained.
Protecting evacuation lighting
Evacuation light fittings should be manufactured from impact resistant material (eg polycarbonate) or be fitted with mechanical protection (eg wire cages).
Periodic testing of evacuation lighting
Evacuation lighting must be inspected and electrically re-tested every 6 months, including a discharge test to ensure evacuation lighting maintains the 20 lx lighting level for at least one hour after the loss of normal lighting. Records of testing should be kept on site or made available for auditing.
Measuring the light level
Determination of the light level cannot be based on a single measurement, but should be taken as an average over the whole route or portion of the route being measured (eg a passage way or stairwell). For consistency the following method should be used to determine if the designated evacuation route achieves the 20 lx lighting level. Readings should be taken:
• with a calibrated light meter held horizontally
• at a height of one metre above the floor
• one metre from the start of the route and at one metre intervals along the route, and
• where shadows are not cast onto the meter
Add all the readings together and divide by the number of readings taken to calculate the average light level. This should not be less than 20 lx. Records of lighting levels should be kept onsite for reference.
A: (25 + 18 + 15 + 12 + 16+ 22) divide by 6 readings = average of 18.0 lx (Fail)
B: (30 + 22 + 18 + 5 +19 + 30) divide by 6 readings = average of 20.7 lx (Pass)
Industry Standard – Electrical installations on construction sites
AS/NZS3012 – Electrical installations – Construction and demolition sites
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