Heating system aromas

It still aromas unquestionably bad though

There is something wrong with our beach house gas furnace; Everytime I turn on the gas furnace it reeks of burnt hair, i guess care about this means there is dust, dirt plus hair deep inside the heater. If the heating unit is too dusty, it will overheat, however overheating means parts wear out plus break, or the gas furnace disfigures itself beyond repair. I want to get rid of the burnt hair aroma for safety reasons plus that it also is disgusting to aroma. Everything I have tried has not worked though; My first attempt was simply increasing the furnace filter in the machine. I got a brand up-to-date HEPA filter to catch even more dust from getting into the system, nope, the aroma still happened. Next, I tried taking the unit totally apart plus cleaning the inner laborings. I jammed our vacuum hose up there, wiped along the edges plus doused the unit in bleach; Still when the gas furnace first turns on, the aroma of burnt hair is floating in our air quality. My last attempt was trying our hand at HVAC duct cleaning. I cleaned the air vents plus then stuck a broom in the ducts. I tried to get as much dust out of the air ducts as possible. I thought it was possible that maybe the heat was going over that dirt plus making the aroma. It still aromas unquestionably bad though. So I either did a bad task, or that is not the issue. Now I am thinking I will need to call an Heating plus Air Conditioning company to solve our issue.
Air conditioning workman