I'll GUARANTEE that if your fan is 20 years old it is NOT the same quality (junk) plastic fan that it seems everyone is selling or providing with the new lasers.
These fans are cheap plastic MJ grow fans that only boost airflow. they don't work with any back pressure. I've a 6 inch one that I bought for use with my fibers. It works, but leaks like a sieve.
I ended up putting it outside and it will pull most vapors out. but it is NOT equivalent to the metal chinese blowers or a HF dust collector blower.
I see more complaints about smoke with laser use than anything else and 99.9% is due to lack of flow OUT.