Confined space – Monitoring Legislative Interpretations

262.06(1) Prior to an employee entering a confined space, an employer shall ensure that a competent person tests the atmosphere of the confined space, taking into consideration the stratification of air contaminants and oxygen to ensure that the atmosphere is within acceptable limits.

262.06(2) The results of a test referred to in subsection (1), including the time and date the test was conducted, shall be documented and posted conspicuously at the entrance to the confined space.

262.061(1) The atmosphere of a confined space is within acceptable limits if

(a) the percentage of oxygen is not less than 19.5% by volume and not more than 23% by volume,
(b) the concentration of an air contaminant does not exceed 50% of the lower explosive limit or lower flammability limit of the air contaminant when the confined space work is cleaning or inspecting and does not create a source of ignition,
(c) the concentration of an air contaminant does not exceed 10% of the lower explosive limit or lower flammability limit of the air contaminant when the confined space work is cold work using non-sparking equipment,
(d) the concentration of an air contaminant does not exceed 5% of the lower explosive limit or lower flammability limit of the air contaminant when the confined space work is riveting, welding, flame cutting or other fire or spark producing work,
(e) the concentration of air contaminants and physical agents meet the requirements of this Regulation,
(f) the concentration or percentage referred to in paragraphs (a) to (e) can be maintained during the period of proposed occupancy in the confined space,
(g) any liquid in which an employee may drown or any free flowing solid in which an employee may become entrapped has been removed from the confined space,
(h) the entry of any liquid, free flowing solid or hazardous substance into the confined space in a quantity that could endanger the health or safety of the employee has been prevented by a secure means of disconnecting the pipes adjacent to the confined space or fitting blank flanges or blind flanges to the pipes adjacent to the confined space, and
(i) all electrical or other equipment and machines that present a hazard to an entrant while entering, exiting or occupying the confined space have been put in a zero-energy state and locked out in accordance with this Regulation.

Question
How is the competent person able to verify that the levels in (a) to (d) are able to be maintained unless they have constant monitoring?

Answer
Constant monitoring is not necessary where there is an established history of the concentration levels being maintained and no change in the equipment or process, and periodic monitoring is done.