Machine safety: Access to danger zone

by Sep 20, 2017Machine Safety

Machine safety: Access to danger zone


For many years, Intervention Prevention inc., has been receiving several questions about access to danger zone. By writing this blog, we aim to make more understandable the regulations and standards dealing with the access to danger zone.

Figures 1 and 2. Example danger zone

Access to hazardous areas may be necessary during certain operations but is prohibited without lockout when performing tasks cited in the section 188 of the ROHS (installing, adjusting, inspecting, unjamming, setting up, decommissioning, maintaining, dismantling, cleaning, servicing, etc.).

Where the employer intends to apply an energy control method other than lockout, the employer must first ensure the equivalent safety by a risk assessment (sec 188.4 ROHS).

Controlling the danger zone is regulated by the section 182 of the ROHS that should be clearly understood.

Figure 3. Access to danger zone

Two situations are to be considered:

  • In the case where no one will have access to the machine’s danger zone while it is in operation, the first option to came in mind is the permanent protector (according to same practical constraints, other types of protectors could be allowed). The permanent protector must be set in place permanently by being bolted or welded; to be removed, protector destruction or tool use is necessary and a lockout procedure should be applied before removing the permanent protector to access into the danger zone. Some employer try to voluntary misinterpret the section 182 by using, for example, loose bolt on permanent protector frequently used, thus, workers can easily have access to the danger zone.
  • In the case where at least one person will have access to the machine’s danger zone while it is in operation, the danger must be controlled beforehand, for this purpose, a set of solutions are proposed in the second part of the section 182 such as interlocking protectors (sec 175) interlocked protectors (sec 176), sensor devices (179), etc.

Figure 4. Loose bolt-easily removable-no need for tools (unauthorized situation)

Figure 5. Bolted protector

The chosen solution must be a result of safety related parts of control system calculation, risk, and process analysis to ensure that it provides the required safety level without altering the practical or functional needs.

For the interlocked and interlocking protector, it is mandatory to ensure that the machine will not restart when they are restored to their initial place.

Figure 6. Door with interlocking protector

The sections 177 and 181, deal with some other protective devices such as two-hand control device, however, this type of design, establishes safe condition for only one person and the danger zone still reachable.

Finally, the ROHS defines two fundamental characteristics to keep in sight while designing protector in the section 187:

1-The protector shall not cause additional risks for workers or;

2-Be itself a source of danger


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Intervention Prévention Inc.

Intervention Prévention concentrates its operations in the field of work safety, offering specialized services following Standards CSA Z462 – Workplace Electrical Safety, CSA Z460 – Control of Hazardous Energy: Lock-out and Other Methods, and CSA Z432 – Safeguarding of Machinery.


137-2020 rue André-Labadie
Beloeil (Québec)
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