Except as otherwise provided in Article 2, nothing in this chapter shall apply to firefighters employed on July 1, 1971, and such firefighters are not required to meet the requirements of Code Section 25-4-8 or Code Section 25-4-9 as a condition of tenure or continued employment; nor shall their failure to fulfill such requirements make them ineligible for any promotional examination for which they are otherwise eligible, affect in any way any pension rights to which they are otherwise eligible, or affect in any way pension rights to which they may be entitled on July 1, 1971. The council shall have the authority to investigate qualifications of, and in its discretion to issue certificates to, those previously trained firefighters employed on July 1, 1971.