Is the fact that my combi boiler isn't venting to the outside dangerous?

Hallo I believe that the word "venting" is refer to the fact that product of combustion is not expelled on the outside of the property. Combi boilers are sealed system, which introduce air to the burner from the flue, and expelled Product of combustion directly outside though the flue as well. There are some security device which will stop the boiler to work if all the parts don't work properly. A "Landlord Certificate" MUST be obtained by the owner of the house, and a copy of it MUST be exposed in the rented house. The certificate is a annual security check which should give you and the landlord peace of mind. I hope that's help Tiziano

Hi I would not use the boiler until you have assurance from the engineer that the boiler is safe and as already advised you have a CP12 I would also advise you fit a co alarm for the boiler mark premier heating

Please provide a little more information. By venting do you mean there is no ventilation to outside? I think if there was a ventilation or flue fault the boiler would be disconnected by the previous engineer. What make and model is the boiler? What are the symptoms? Has it been disconnected or a safety notice issued? The landlord has a legal duty to ensure that the appliance is safe.