Sounds like LH4965 (rather than LH2965...)
There's been an ongoing issue with 146's, and nasty smells entering the cockpit / cabin during t/off. IIRC, there's work going on now to work out what it is causing the problem; suggestions that it's due to the location of the air inlets relative to the engines.
I've certainly had a couple of smelly t/offs in 146's (not just LH's). Always safer to come back down again, but I don't think any of them have ever resulted in mid-air danger.