How does leak dye work?

Q: How does a dye test work to locate a refrigerant leak in my system?

It’s fairly simple, actually.  When there is a large leak, you can easily see the buildup of refrigerant oil and an electronic leak detector can verify the location of the leak.  When there is a small leak, however it becomes difficult to locate as there is generally just a small amount of refrigerant residue.  In these situations, our technician injects the system with a dye, which runs through the system.   When the system has a small leak in it, the dyed refrigerant comes out leaving a residue that is normally transparent to the human eye.  With the dye, we can see this refrigerant to determine where the leak is located.
You can see the bright green areas in the image below.  This is the residue of the dye treated refrigerant that has leaked out.