Heat mats are for germination only. Never keep germinated seedlings on heat mats. It can kill the roots quickly.

Same goes for domes. They are never to be left on once germination occurs - better to not even use them in the first place. Nothing causes damp-off to develop faster than domes left in place after germination. For plants, air circulation is vital, humidity in the air is not.

And just because the surface of the soil looks dry doesn't mean it is actually dry. The surface moisture content isn't relevant. It is the moisture at the root level that counts.

Numerous discussions here about all this that the search will pull up if you want multiple opinions.

Dave

Dave, good thing I read your reply just before going to bed last night. I went back downstairs, turned the heat mat off and removed the dome cover. One of my pepper varieties hadn't germinated yet so I hope it still does. I made the mistake of mixing varieties in six-cell packs. The yellow peppers on the LHS of the cell packs germinated but the orange peppers on the RHS of the same cell packs did not germinate yet. Yet another lesson learned.

Yep - no mixing varieties in the same cell packs. If necessary just cut the cell pack into 3 packs.

Dave