dont forget to do a monthly inspection on those extinguishers to check for pressure, hose cleanliness and rust on any pressure part. I would do the upside down shake, rattle and roll at least every month also. At the office we send them in for service every 12 months (we have the CO2 cartridge type ) and the service tech takes all the powder out and replaces it, checks the co2 cartridge and then recertifies it with a new sticker. I dont think the powder would be good for that long on a tractor without settling and compacting. I dont have one on my tractor, but I think I will get one for it. Maybe a nice CO2 type. NO powder settling problem with that. Having seen many powder extinguishers used to try to put out a paper fire, I would not trust them to put out burning leaves either. I watched a guy use up a 20lb. ABC powder type on some burning burlap bags and the fire never was put out. The bags were on some grating so it just kept feeding the oxygen to it. A good CO2 would have snuffed it completely.