If you feel that the compact cleaner produces too much ozone, because it basically has finished cleaning, and you forget to turn off the machine, there is no danger; it is not possible to produce a surplus of ozone with model MAC500.
The smell limit for ozone is approx. 0,02 ppm. After this, the ozone begins to smell like a Xerox machine, that has copied many copies in a row. The Danish Working Environment Service has a limiting value for ozone in a working area which is 0,1 ppm. This means 20 times the amount that has to be present for smelling ozone. The MAC500 cannot produce enough ozone to exceed the limit set by the Danish Working Environment Service