Section 7.4 - Product testing(a) All products submitted for approval under this part shall be tested using the test procedures specified in the appropriate subpart unless MSHA determines, upon review of the documentation submitted, that testing is not required. Applicants shall maintain records of test results and procedures for three years.(b) Unless otherwise specified in the subpart, test instruments shall be calibrated at least as frequently as, and according to, the instrument manufacturer's specifications, using calibration standards traceable to those set by the National Bureau of Standards, U.S. Department of Commerce or other nationally recognized standards and accurate to at least one significant figure beyond the desired accuracy.(c) When MSHA elects to observe product testing, the applicant shall permit an MSHA official to be present at a mutually agreeable date, time, and place.(d) MSHA will accept product testing conducted outside the United States where such acceptance is specifically required by international agreement.53 FR 23500, June 22, 1988; 53 FR 25569, July 7, 1988; 60 FR 33722, June 29, 1995