7.—(1) A daily maximum running 24 hour mean is a mean which is calculated on a daily basis, yielding one daily maximum running 24 hour mean per day. The daily maximum running 24 hour mean for a particular substance at a particular location for a particular day is the maximum of the 24 running 24 hour means recorded for that substance at that location during that day.
(2) For the purpose of the calculation of a daily maximum running 24 hour mean—
(a)a running 24 hour mean is a mean which is calculated on an hourly basis, yielding one running 24 hour mean per hour, and the runnning 24 hour mean for a particular substance at a particular location for a particular hour is the mean of the hourly means for that substance at that location for that hour and the preceding 23 hours;
(b)“day” means the 24 hour period commencing immediately after midnight, Greenwich mean time.