I guess they considered us Flight Engineers to be expendable when it was certified.
The tube is from the "Minimum Equipment Bay" and you are going to sniff a little bit of electrical burning.
I doubt there would be enough to cause permanent damage.
I've used my nose many times when looking for faults in systems.
I remember many years ago when spannering on a Viscount betweem Muscat and Bombay, there was a smell of electrical burning. It took about 2 seconds to discover it was the HF transmitter that was pouring smoke due to being stuck on transmit. CB pulled, problem solved.
And of course we were 2 hours from the nearest airport.