Final answer:
To effectively clean smoke contaminated exterior masonry, detergent solutions with phosphates and industrial-strength cleaners with quaternary ammonium compounds are used. Old methods, like dry-cleaning solvents, are no longer recommended.
Step-by-step explanation:
Effective cleaning methods for smoke contaminated exterior masonry surfaces are achieved by using detergent solutions containing phosphates, such as products like Finish, and industrial-strength cleaners containing quaternary ammonium compounds. These cleaning agents are capable of removing soot and other residues that are typically difficult to clean. It's important to note that previously used methods like dry-cleaning solvents and blasting with materials like fire extinguisher systems foaming plastics are no longer recommended due to their potential hazards and ineffectiveness in dealing with smoke contamination on masonry.