I tested some dust for lead using a 3m lead check swab. The test was negative, and I left the testing fluid on the surface for several days because I hadn't gotten a chance to clean it up. I know it was orange minutes after testing, and also orange a couple days after testing. It's maybe a week after testing now and I just found that it has turned pink. Does this mean lead is present?


The 3M site says this

3M™ LeadCheck™ Swabs have no shelf life. Unless the ampoules/vials are cracked, they will have an indefinite shelf life.

In other words, once the vial is broken (which you did to use the tester), it does indeed have a shelf life

  • I agree, if the op is concerned scuff the surface a bit deeper and retest with a fresh kit, their may be 2 or more layers of lead free paint on top depending on the age of the home and how often it was painted.+ – Ed Beal Oct 23 '19 at 14:20

Not necessarily, it probably means the fluid has oxidized over time.


The fluid is only good for 30 seconds. After that, whatever is says is meaningless.

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