(a) Respirators described in subparts H through L of this part shall be classified, where applicable, as approved for use during the following prescribed service times:
(1) Four hours;
(2) Three hours;
(3) Two hours;
(4) One hour;
(5) Forty-five minutes;
(6) Thirty minutes;
(7) Fifteen minutes;
(8) Ten minutes;
(9) Five minutes; or
(10) Three minutes.
(b) Other service times may be prescribed by the Institute.