Safety nets are installed below elevated work areas to reduce the distance a worker can fall. They are designed to progressively deflect or stretch – if a fall occurs, the net absorbs the impact and provides a soft landing, reducing the likelihood of injury.
The greater the height from which a person falls, the greater the impact. Nets must be able to deflect enough to absorb all the energy from a fall at the maximum fall height they are designed for.
Clearance distance below the net
The clearance distance is the distance below the net that must be clear of objects so that a person falling does not strike an obstacle.
Safety net components
Safety nets consist of different types of ropes, including:
● mesh ropes – a minimum of three separate strands of rope braided in such a way that they cannot unravel
● border ropes – a continuous rope that is threaded through each mesh around the perimeter of the safety net
● tie ropes – fasten the safety nets to structural elements and/or anchor points on a structure
● coupling ropes – join nets together when more than one net is needed
Knotted vs knotless nets
Safety nets may be knotted or knotless in either a square or diamond mesh arrangement. Knotted and knotless nets react somewhat differently under impact.
When a load lands on a knotted net, the knots tighten near the impact. The tightening is permanent and reduces the amount of energy the net can absorb in future impacts.
Knotless nets do not lose absorption capacity following an impact and they also tend to result in fewer facial or graze injuries when a person falls into them.
Installing safety nets
Safety nets may be attached either with tie ropes or karabiners to structural elements such as trusses, rafters and top plates, or to specifically designed anchor points on the structure being netted. They must not be attached to purlins, battens or non-structural components such as gutter supports, pipework or electrical service installations.
The recommended maximum spacing between fixing locations is 1.5–2 m. Fixing locations and anchor points to which safety nets are fastened must not have sharp edges that could damage or cause abrasions to any of the ropes. Nets must be easily accessible to carry out a rescue and to remove debris. They must not be used for storage, as a work platform, or for providing access to a work platform.
As well as catching a falling person, safety nets will also catch falling debris. Debris can damage the net and becomes a hazard if left in the net, as it may cause:
● injury to a person who falls
● the net to overload and deflect too much
● the net to sag and increase the fall distance
When debris falls onto a safety net, work should stop immediately both above and below the net, the debris should be removed and the net checked for damage before work continues.