A red tag is also referred to as a warning tag and is placed on a furnace or hot water heater by a McAfee Technician to indicate that the equipment is no longer safe to operate and either needs to be repaired or replaced. A McAfee Technician who identifies a warning tag situation is required to turn off the gas and electric as a safety precaution to protect the residents of a home or business.
One of the main reasons a warning tag is placed on a furnace is when a defective heat exchanger is identified. A defective heat exchanger can be a hazard because it can release carbon monoxide, an odorless and colorless gas that can cause serious health problems and or death if undetected. Carbon monoxide is harmful because it rapidly accumulates in the blood, depleting the body’s ability to carry oxygen.
For further info on Carbon Monoxide and its effects in the body. Visit: http://www.mcair.com/resources/carbon-monoxide-the-silent-killer/