What is the maximum number of persons permitted to work on a single current of air?

The maximum number of persons permitted to work on a single current of air being set at 80, with a permit, is based on safety regulations designed to ensure the protection of workers in environments where there is potential for hazards such as poor air quality or oxygen deficiency. This regulation is significant in the context of mining or other confined spaces, where air quality can rapidly change and affect the health and safety of those working.

In this case, requiring a permit for a workforce of 80 suggests that there are strict controls and assessments in place to monitor the conditions of the air, ensuring it is safe for all individuals present. This emphasizes the importance of managing air quality, as larger groups could increase risks, requiring coordinated safety measures.

The other options either propose lower limits or conditions that do not align with the established guidelines, making them less applicable in this context. The choice of 80 persons serves as a clear benchmark for operational capacity under regulated safe practices.