First of all you need to immediately report this situation to the fire marshall; they will mandate that your landlord take immediate action. Additionally, every residential lease has what is called a "warranty of habitability". This means that a landlord must supply a clean and safe premises for you to live in. Since you are dealing with a legitimate safety concern, you have some options as to what to do and breaking your lease is one of them. However, there are strict guidelines for this; if you don't follow them you could be held liable for paying the remaining lease term.At this point either consult with a local attorney or a tenant's rights organization.