Can I occasionally turn of the mercury vapor bulb?

[Theia]

Hi I live in England and have a corridor which had 3 windows I open fully whenever possible. I wondered if I can turn the uvb vapour bulb off sometimes. I worry about the vapour bulb but I don't have access to housing that has longer safer bulbs. I take him downstairs to the gardens once or twice a week more if its hot weather. How many hours does he need approximately in our temperate weather to warrant turning uvb light off

 

[wellington]

If he gets natural sun light 3-4 times a week you do not need artificial uvb. However, they always need a correct basking temp except at night.

 

[ZEROPILOT]

I would not only turn off the MVB lamp. I'd unplug it and toss it into a garbage can.
MVB often do more harm than good.
If you will be using actual sunlight. Keep in mind that almost no UVB transmits through a glass window of a window screen.