Barometers and barographs should be checked as frequently as possible against standard
instruments on shore at least once every three months. A permanent record of all such
checks should, if possible, be attached to the instrument, and should include such information
as the date of the check, temperature and pressure at which the check was made. It is
particularly important that barometers and barographs be checked as frequently as possible,
because of possible zero drift, especially when the instruments are new.