‘Should I order radon if there is a mitigation system already in place?”
The EPA recommends retesting your home, even with a radon reduction system in place, every 2 years. If the seller cannot provide a test result within 2 years it is recommended to order a radon test with your home inspection.
Generally radon reduction systems, when they are installed well and are working properly, reliably reduce radon to safe levels in the home. However, there are two questions to ask with homes with mitigation systems in place (see below). A negative test result is still worth the cost of the test if it gives the buyer peace of mind.
Was it installed properly?
We have tested homes with radon reduction systems that have come back high– typically this is because the system was not installed correctly (missing fan, timer on fan, etc…) or because the fan had failed or was turned off somehow. For years there was this idea in our industry that ‘passive radon reduction systems’ or systems without fans would reduce radon to safe levels in the home but over time we are seeing that this is not the case– radon reduction systems need to be under negative pressure (fan powered) to work reliably.
Was it maintained properly?
These systems need maintenance and repair like any thing else in the home. The components that fail most often on these systems is the fan and the manometer (pressure gauge) which typically have an 8-12 year life expectancy. Keep in mind that the manometer only indicates that the system is under pressure and does indicate the radon levels in the home. If the fan is failing or has failed then radon levels will be higher in the home.