Which of the following is NOT a respiratory hazard associated with fires?

Aspartame is a low-calorie sweetener often found in various food products and is not associated with fires or respiratory hazards. Unlike the other substances listed, aspartame does not generate harmful gases or particulates that would pose a risk to individuals' respiratory systems during fire incidents.

In contrast, carbon monoxide, hydrogen cyanide, and soot are all significant hazards in fire scenarios. Carbon monoxide is a colorless, odorless gas that can cause poisoning, and is produced from incomplete combustion of organic materials. Hydrogen cyanide is another toxic gas that can be released when materials like plastics and synthetic fibers burn, posing severe health risks. Soot, which consists of carbon particles from incomplete combustion, can lead to respiratory issues when inhaled. These substances underscore the importance of understanding and identifying various respiratory hazards when combating fires.