nes227--yes, welcome, but let me put your mind at ease a bit about smoking and meat safety.
1. There is a legitimate concern that bacteria could be in your meat. Since basically nothing lives over 140F, one should cook their meat before eating it so that ALL of the interior comes to at least 140F.
2. That said, meat sold commercially today has additives that kill bacteria regardless of temperature. The classic ones are sodium nitrate and sodium nitrite. Sodium nitrite has huge financial advantages in that it keeps meat looking pink/red and "fresh" much longer so you needn't worry about commercial meat not having enough of it! (If you're a hunter who cooks fresh kill, disregard most of what I say.)
3. Bacteria don't like it nippy either. Hence, refrigeration was a huge advance in preserving meat. And if you're colder than water's melt point ("freezing the meat") it will essentially last forever.
4. There is also bacteria in the air...think of the breeze wafting over that pile of dog poop in the neighbor's yard...not a lot, but "it's in the air". This the reason we minimize the time meat is in the "danger zone" of 40-140F. The bacteria can land on the surface and multiply (lots of oxygen available) and the preserving effects of the nitric acid breakdown products of the nitrite underneath won't be adequate.
5. But it's a temperature AND time effect. Throwing a cold steak on an 800F grill may prevent any bacteria from landing and growing on the hot (bottom) side but the top side of the meat is still cool to the touch...and your "touch" has plenty of bacteria too. But after a few minutes you're ready to flip the steak and a little later a meat thermometer will show >140F throughout and a few minutes you safely eat the meat...at about 100F. So a good rule is that meat should not reside in the Danger Zone for longer than ~15 minutes. But you can never avoid the Danger Zone completely.
6. It appears then that cold smoking at <140F for hours at a time would be bad then, right? Well long before refrigeration and sodium nitrite, mankind learned that smoke itself has a preservative, bacteria-killing effect. (If I recall, it's nitric oxide in the "smoke ring" that works the magic.) The trick just seems to be: do such smoking in a closed space. Don't have smoke on the bottom side of your meat and "fresh air" (which isn't) wafting across the top like on an open grill. So smokers have doors. Use them. (Besides, if yer' lookin', y'aint' cookin'.)
7. The other important aspect of "cold smoking" is that even without electric fans, the natural draft of cold air being heated and rising results in a "positive pressure" within the smoker. So your doors don't have to be "air tight"...there's a pressure inside resisting that bacteria-laden air from entering.
8. And of course in this forum we're talking about pellet grills and smokers so we're NOT talking about cold smoking. But the point is if in Smoke mode you occasionally drop below 150F or even below 140F, well, people have been doing that for centuries, and in much less sanitary conditions than us. Still, it's good practice (and saves time) to get to know your cooker and avoid low temps. If you like to cook at 220F and you find in Smoke Mode you drop to 150F in 20 minutes, then set your smoke time to 20 minutes, not the 1 hour the manual might recommend. Most all controllers revert to your set point when the smoke mode time is up so they really are "set and forget".
Anyway, I hope this puts your mind at rest. Occasional swings under 200F are nothing to worry about in a closed, smoke-filled cooker. There may be things about this hobby (the quantity of fat consumed, general colorectal cancer risk, etc) that bears some long-term health risk, but getting botulism isn't one of them.
