Hi Cameron

The intention behind the suggestion of breaks when wearing any respirator is ergonomic and fatigue related. Unpowered respirators are very well known to create earlier fatigue to the wearer than powered respirators because of the effort required to actually inhale the air through the filter - incidentally, you don't identify what the activities being undertaken are, what forms of filter are provided, nor what the respirators are worn to protect against.

Although the manufacturers go to great lengths to minimise the effort of inhalation and exhalation, there is inevitably a cumulative load placed upon the respiratory system. The break should be considered in conjunction with the activity, the ambient environment, any PPE required, the type of respirator [how easy is it to breath after approx 15, 30 & 45mins] and the physical condition of the wearer as well as any other relevant points. The work controller must undertake a suitable RA and decide what an appropriate break length would be - incidentally, the use of the term "break" is meant to indicate a change of activity that doesn't require a respirator rather than a "tea-break" but the RA will determine which is most appropriate in your circumstances.

There are considerable very technical research documents on the use of respirators; but very few actually address the issue of fatigue in a sufficiently direct way as to be applicable in the workplace without a degree of competence in the topic although the HSE has produced some publicly available documents on fatigue.

I know that I haven't actually provided a number in minutes for the break; but that simply isn't possible without considerable in-depth risk assessment - sorry.

Frank Hallett