Demron fabric has been tested by several DOE labs for effectiveness against ionizing radiation.
Other BC suits are heat sinks. With very little aktivity, heat will build up in the suit and it will continue to climb at rest. Because they are insulating, they cannot be cooled externally. Only the Demron suit reduces heat stress production, passively coold, and the first responder can be externally cooled without the need to be de-gowned.