Gas smell NSTAR says everything is fine

I am a new tenant and noticed from the start a faint gas smell in one bedroom. I called NSTAR, they ran their gas detection meter in the room but couldn’t find anything. They then went to the basement and found that an old gas line that was probably one used for gas lighting in that room was never disconnected and was leaking. My landlord had a plumber disconnect it right away, then NSTAR came back to inspect, said everything looked good, and turned the gas back on. The next morning after having the windows closed I smelled it again, and called NSTAR right away. They came out, said they could find nothing, and said it was probably residual gas from the line which should go away but wasn’t dangerous because the pipe had been disconnected. That was several days ago, and I’ve been keeping the windows in that room open for aeration. Last night, I tried keeping the windows closed with fingers crossed, and low and behold this morning the has smell was there again. When can I expect it to go away? I am worried that the nstar guys were wrong and there is a gas leak somewhere else but I am not at all knowledgeable in this field, and my husband and landlord feel satisfied with NSTAR’s explanation. To top it off this is my kids’ room. Does it make sense to accept the explanation that this if residual has that will eventually go away? How long would that take?

If you continue smelling the gas.I would contact my local fire department.they will make sure someone will spend some time looking for the source. document everyone that you contact.