Bulbul asked 12 months ago

I would like to ask you a question about dogs in Islam. 
I work at a office and a small dog lives there. The dog stays overnight.
I don’t know whether the dog touches my table or my chairs, such as I don’t know if the dogs saliva   is on the table. 
When I come in the morning the area seems dry.
Once the Saliva or urine is dry, do I still need a wash my hand and clothes? 
Even though I don’t know if the place has been touched by the dog or it’s saliva.
This problem is getting worse and worse for me. I need a clear answer. Please can you help me with?