Simply put, wet cleaning is applying a chemical onto a coil, letting it sit for a certain amount of time, and rinsing it with water. However, evaporator and condenser coils are made from various materials. In commercial spaces, coils may be made of copper and stainless steel, while residential spaces may be coated, microchannel, or copper mixed with aluminum and other metals

Determining which material makes up the coil should be done before attempting to wet clean, as chemicals can cause massive damage if misused. “Read the label,” Rizen said. “Know what product you’re using, what’s in it, proper dilution ratios, and the dangers of skin contact and inhalation.”

Once the right chemical solution is chosen, there are different approaches for wet cleaning both the evaporator and condenser coils. “Water control is key with evaporator coils,” Rizen said. “Residential drain pans, for example, are often only an inch deep, which means they fill up fast, and any overflow pours out the bottom of the system.” Overflowing can mean water in the next room, soaked drywall, or even ruined system electronics, which can create additional problems for a technician.

For condenser coils, though they are outside and may be unimpacted by potential overflow, there are other potential dangers from misuse. “It’s more important with condensers to get the chemicals diluted, flushing them with plenty of water,” Rizen said.

Improperly diluted chemicals can have far-reaching effects on particular spaces. For residential systems, chemicals can seep into soil, kill grass and other vegetation, or remain a hazard for people or pets who may occupy the area. For commercial properties, chemical run-off can damage the roof itself...