There are several ways to recognize the presence of a hazardous substance or the warning signs of a hazardous substance release. The shapes of containers are often a clue that they may be storing hazardous substances. For example, large drum barrels or a reinforced (e.g., ribbed) tanker car are often used to transport and store chemicals or hazardous wastes. Also, the federal government has a system for labeling containers used to store or transport hazardous substances that uses colors and symbols to designate potential hazards.
Although not the preferred method, one's senses may detect hazardous substances: a foul odor, visible gases or unusually colored flames, or the increased pitch of a relief valve on a pressurized container. However, do not assume gases and vapors are harmless because they lack odor -- odorless gases or vapors may also be extremely harmful. Other common-sense signs may warn of danger. For example, people running from or suddenly collapsing in a hazardous material area, visible signs of a leak, or gas clouds emanating from a facility or vehicle all suggest the risk of a hazardous substance release. It is always best to be cautious and treat potential releases as real threats involving hazardous substances.