These milder/moister temp trends in central PA can wreak havoc. Even though my wood is seasoned 5 years or more (top covered), the mild, damp atmospheric air meeting that hot flue gas at the spark arrestor causes issues, especially this time of the year when I'm burning "idly" so I'm not cooking everyone outta the house. I noticed the fireplace kinda acting overly lazy so I went ahead and did my mid-season inspection a few weeks early (usually do a cleanout/inspection right around Christmastime). The spark arrestor was the worst it's ever been. Not completely clogged but enough so that it caused a very lazy draw. The clogged screen was all dry and easily crumbled off. I should've taken some pics but didn't have my phone on me during the inspection. Cleaned the cap thoroughly and swept the flue, which had literally nothing in it. It was basically completely clean, brush easily went right down and right back up with zero resistance. So just a reminder that even well-seasoned wood cannot totally eliminate issues at lower flue temps, namely at the spark arrestor during moist and mild seasons.....
Yup, get just the right (wrong) temp and humidity, buildup can happen pretty fast, especially on a cap with finer holes. Fortunately the cap on the flue that is used 99% of the time here has larger holes (like 1" x 3/4") and has never had a buildup, at least not yet, but it's been 12-13 years now, so...
The screen on my cap is stainless steel and has 1/4" holes, hence the reason it clogs up pretty fast when conditions are just right.
Mine does the same... I get on my roof and use a long, skinny tree to knock the creosote off. Sometimes have to do it a few times a year.
The irony for me is I'm so OCD about seasoning my wood (as are most of us in here). The bottom line is there are situations where no matter how "by the book" we go, you will have nuances like this crop up. The little voice in the one part of my head says "take that stupid spark arrestor out" but I leave it in because in the end you're still gonna get that buildup on/in the cap and it will end up as bigger chunks that if left go can cause a much bigger issue. The spark arrestor needing periodic cleaning is a good thing because it beckons you to go ahead and sweep the flue while you're at it, preemptively stopping other issues from being "ignored" and ensuring that you are burning properly, so I guess it's a good thing?
