Mo. Rev. Stat. § 260.545: Providing assistance at request of department, political subdivision or volunteer fire protection district, liability for actions, when.

Any person who provides assistance, including equipment or materials, at the request of the department or a political subdivision or volunteer fire protection district or by previous agreement with the department or political subdivision or volunteer fire protection district in the event of a release of a hazardous substance shall not be held liable in any civil action for damages as a result of that person's acts or omissions in rendering such assistance. Nothing in this section shall relieve any person from civil damages in the following circumstances:

(1) Where the release referred to is the result of the person's having control of a spilled hazardous substance;

(2) Where the person rendered assistance for payment beyond reimbursement for out-of-pocket expenses or with the expectation of such payment; or

(3) For acts or omissions which result from intentional wrongdoing or gross negligence.