Gas boiler and ventilation / air flow in the room

[what..the?]

We are having problems with pest's as in rats/mice in our garage the main problem is that below the 'up and over' garage door is a massive gap.

The driveway slopes down in tarmac to meet the garage floor which steps up so the water does not flow inside off the drive, the step is approx 2 inches high. The garage door doesn't meet with the floor inside the garage or the tarmac outside. There is approx 3 inch gap underneath which helps ventilate the garage but allows the pests in. We do not keep any food stuffs or bird seed etc in there so we are not attracting the pests as such. We would like to place a long plank of wood or such in the gap and secure it, we only rent the property so we cannot make permant changes, and if we ask them to fix it they will fail to ever get round to it.

But there is a small room/porch at the back of the garage down 2 steps this connects the garage to the house via a back door. The gas boiler is on the wall in this porch area. Is there a gap under the garage door because of this and potential ventilation and/or would there be problem if we block up the gap. I believe the boiler from memory has some sort of extenal vent behind it through to outdoors. But does a gas boiler need certain ventilation???

As help please.

[gasman]

All Gas burning appliances need ventilation to operate safely but they all get their air in different ways so it is impossible for us to help you without knowing the KW of the boiler so as to work out its ventilation requirements. And the type of appliance needs to be determind aswell is it an open flued appliance, a room sealed appliance or a balanced flue appliance ??? If you are not sure then simply tell us the make and model etc... of the boiler then we should be able to help you out.

[what..the?]

Thank you so much gasman for your help. Yes I haven't got a clue quite frankly about what type of gas boiler it is but I will have a look tonite and get back to you.

Thank you again for your time.

[gasman]

OK I will check back later.

[gasman]

Did you check on the make and modle yet ???

[what..the?]

I am so sorry gasman for the delay, I am so grateful for your time and helpfulness but I have the worse memory at the moment, it was only this morning I thought about it again and you waiting and I thought I would pop out to the garage to have a look, but forgot and ran out the door late for work instead I am so sorry.

I will have a look tonite I promise and will post it tomorrow morning. If you have the time I would be more than grateful for your assistance.