We seem (like many in our neighborhood) to have a nagging number of
Carpenter ants around our New England house.

We bought Home Depot's "best" which supposedly "kills on contact",
however, the ants seemed to just swim through the stuff.

What are your recommendations for the most effective *consumer* spray
that effectively can be used against Carpenter ants? (both inside and
outside).

My perhaps faulty assumption is that anything sold nowadays to
consumers will be reasonably safe.