General principles for work at height - Petzl Belgique

General principles for work at height


  • Carefully read the Instructions for Use used in this technical advice before consulting the advice itself. You must have already read and understood the information in the Instructions for Use to be able to understand this supplementary information.
  • Mastering these techniques requires specific training. Work with a professional to confirm your ability to perform these techniques safely and independently before attempting them unsupervised.
  • We provide examples of techniques related to your activity. There may be others that we do not describe here.


• You must have understood and retained the information from your products' Instructions for Use to be able to apply the techniques presented in this document

• Gaining an adequate apprenticeship in appropriate techniques and methods of protection is your own responsibility. Petzl solutions are given for information only, with no guarantee of their effectiveness in your specific working situation. The relevance of these solutions varies by context, so always do your own risk analysis in the field

• Mastering the techniques presented here requires specific training and practice; work with a specialized organization for all training activities

General information on falls

The risk of falling is a key concept to master when working at height. The severity of a fall depends on independent factors:

• The weight of the user, including his equipment:

The greater the weight, the more energy to be dissipated during the fall.

• The length of the fall:

The longer the fall, the more energy to be dissipated during the fall. The risk of hitting an obstacle is also greater.

• The position in relation to the anchor:

When the worker moves above his anchor, the severity of the potential fall increases. The fall factor concept is sometimes used to describe the position of the worker in relation to the anchor and the severity of the fall. This concept applies to climbing, restraint, or work positioning situations, when a dynamic rope lanyard is used.

Precautions for the type of system used:

the Instructions for Use specify the limitations for use of equipment, particularly in terms of length of a fall and the position of the worker in relation to the anchor.

Anticipating rapid evacuation

• Limiting the effects of inert suspension:

In case of a fall where the worker loses consciousness or is incapacitated, inert suspension in the harness presents a mortal danger requiring urgent treatment. Work teams must be equipped and trained to quickly evacuate an injured team member.

• Evacuating a victim without assistance:

Procedures for evacuating workers should be determined whenever a new work site is established.

Releasable systems can be created during installation of working ropes to allow evacuation from below.

Working alone must be prohibited: a worker may find himself alone at height, but at least one person trained in evacuations should be present and equipped on site.

1. Restraint

A restraint system limits the work zone, keeping the worker from entering an area that may present a risk of falling. This system is not designed to arrest a fall from height.


2. Work positioning

A work positioning system supports the user and allows him to position himself precisely, supported or suspended. This system is not designed to arrest a fall; the user must be under tension on his positioning system.

The work positioning system must be completed with a fall arrest system.

Work positioning.

3. Fall arrest

The fall arrest system is a belay system that is independent of the progression or work positioning system, connected to the A (fall arrest) attachment point of the harness.

The fall arrest system doesn't prevent a free fall. Its role is to arrest the fall while limiting the impact force experienced by the user. It must therefore be used with enough clearance to allow for a free fall.

Fall arrest.
Fall arrest.

• Limiting the impact force: absorption of the energy of a fall:

A fall arrest system must ensure that the impact force experienced by the user does not exceed 6 kN.

A fall arrest system usually has an energy absorber. It is designed to limit the impact force for a predefined maximum fall length, under the conditions specified in its Instructions for Use.

A dynamic rope lanyard has a low capacity for energy absorption. Its use requires great caution: reducing the length of a potential fall and staying in a work position below the anchor.

A webbing lanyard or a cable, with no capacity for energy absorption, can not be used to arrest a fall.

Example for 80 kg

JANE or PROGRESS lanyard without energy absorber

Fall factor 0.5

Fall factor 1

Fall factor 2

JANE or PROGRESS lanyard without energy absorber.
JANE or PROGRESS lanyard without energy absorber.

Lanyard with ABSORBICA energy absorber

Lanyard with ABSORBICA energy absorber.

• Distance for fall arrest and clearance:

Clearance is the minimum amount of clear space below a fall arrest system that prevents the user from coming into contact with any obstacle in the event of a fall.

The required height varies with the system employed (energy-absorbing lanyard, mobile fall arrester...), with the user's weight, and with his initial position in relation to the anchor.

Clearance takes into account:

- The stopping distance of the mobile devices or the length of the lanyard (A)

- The tearing length of the energy absorber (B)

- The average height of the user (C)

- A safety margin (D)

- The potential elongation of the support (rope stretch) (E)

A clearance estimate is proposed in the Instructions for Use for each device.

Distance for fall arrest and clearance.