Public records shall be available for inspection and copying, by appointment, during the customary office hours of the department for a minimum of thirty hours per week, except weeks that include state legal holidays. For the purpose of this chapter, the customary office hours shall be from 9:00 a.m. until 3:00 p.m., Monday through Friday, excluding legal holidays. RCW 42.56.090. Such inspection and copying may be postponed if, in the department's opinion, it would interfere with duties related to an emergency at a regional office or the fire control division in central headquarters.