single floor, completely square design. Lots of scientists, security guards, and bio-operators and a mix of other types. It also tends to have lots of mechanical guards that fight the zombies. sometimes you just end up pulping all the corpses and not actually fighting that much. There are very few turrets to worry about and those mostly get destroyed by the zombies.
Loot is mostly chemistry materials with some containing mutagens (supposedly the ones with subway only access, but i cannot personally verify). sterile CBM drops from the scientists are fairly numerous (and if you enjoy 45 minute dissections for few rewards, go for it).
These types of labs are either accessed via an elevator from an above ground building or via subway access only. there are a LOT of these underground, with many only having the subway access. they do not have lower levels and have none of the barracks/library/prisoner-containment type rooms. No autodocs. They also do not have a guaranteed finale room like the older labs.