In the last 6 weeks we have noticed a strange smell in our house, by the frontdoor and passage way. The smell comes and goes but can get quite strong. I can only describe it... don't laugh, as smelling of someone smoking cannabis. However no body in the house smokes. I first thought that it may be the neighbours and the smell was drifting through the walls? However now I don't think it is. I've been sniffing everything to track down the smell but to no avail. What could this be? I don't think it's gas, the central heating is off and why is it stronger by the front door and passage?
The house is a 1930's terrace, in good condition and we have been living here for the past 4 years. Please help.

Scents travel. It might be your next door neighbor, it might be someone down the road. Maybe keeping a log of it might help you determine the cause.

Yes, keep a log of when you detect the smell.
Could it be when a neighbor arrives home from work and smokes marijuana?
Could it be from house plants, inside or out?
Only when it is warm or wet?
Throw rug outgassing in heat from sun.

Have fun tracking it down and please tell us.
Thank you.
Robert