Performed furnace maintenance on 2000 lennox heater. Upon arrival homeowner stated that system has not been maintenance since 2019. I mentioned in the previous company was maintaining System although he was not satisfied with the work. Perform safety inspection on unit 1. Static pressure on the heater was 0.73 which is two times over the 0.5 it is rated for this is an indication of air flow restriction inside of the air duct system 2. System was tripping high limit switch due to clogged filter inside of 1 inch filter rack. Recommend filter swap every 1 to 3 months with a replaceable throwaway filter 3. Gas line is not equipped with drip leg 4. System is not equipped with surge protection in the case of a power outage thunderstorm etc. 5. Air scrubber bulb Is defective and burned out. Recommend catalyst is replaced to get air scrubber back to proper efficiency and sanitization of home Discussed and informed the full condition Charles 21 year old heater. At this time Charlie is not prepa