Which agency is abbreviated CDA in Monsters, Inc.?

The agency abbreviated CDA in Monsters, Inc. is the Child Detection Agency.

The CDA is Monstropolis's emergency-response organization for incidents involving human children, who are believed to be dangerously toxic by the monster population. Its agents wear distinctive yellow protective suits, helmets, and breathing equipment, reflecting the city's extreme fear of contamination.

The agency becomes central when Boo follows Sulley and Mike back into the monster world. After Boo is discovered at Harryhausen's restaurant, the CDA seals off the building and performs a large-scale decontamination operation. Celia and the other exposed monsters are treated, while the restaurant is engulfed by a protective energy dome.

A common mix-up is confusing the CDA with a defense or law-enforcement agency. Although its agents behave like a heavily equipped tactical unit, the name specifically refers to detecting and containing human children. The acronym is also a joke built around the film's exaggerated premise that children pose a biological threat to monsters.