A new radon system is only as good as the proof that it works. The post-mitigation retest provides that proof, but only if it is done correctly. Timing, kit placement, and house conditions all affect the result. This guide gives York homeowners a simple plan for a fair retest. The answers below come up in almost every visit.
Official source: EPA radon testing information
How do I retest for radon after a mitigation system is installed?
Wait until the system has run for at least a full day, then place a short-term test kit in the lowest lived in level of the home, two to six feet off the floor, away from exterior walls, windows, vents, and drafts. Keep windows and doors closed for at least twelve hours before and during the test. Many York homeowners retest within the first month after install, then every couple of years after that.
Getting the Timing Right
The system needs a little time to change conditions under the slab before you test. Many guides suggest waiting at least a full day after the fan starts. Testing within the first month is common, while the installer can still make adjustments easily if needed.
Watch the weather. Strong storms and high winds can affect short-term radon readings. If a big storm is coming, it may be worth waiting a few days.
If the retest is part of a home sale, the schedule may be tighter. Talk with the contractor and both agents about who places the kit, when, and how the house will be kept closed. Clear agreement up front avoids arguments about the result later. Ask the contractor to point these details out during the visit so you know what to watch for later.
Placing the Kit Correctly
Put the kit in the lowest level of the home that is used, or could be used, as living space. In a finished basement, that is the basement. If the basement is unfinished and only used for storage, the first floor may be the right spot.
Set the kit two to six feet above the floor, at least a few feet from exterior walls, and away from windows, doors, vents, fireplaces, and sump pits. Avoid kitchens, bathrooms, and laundry rooms, where humidity and exhaust fans can skew the result.
Do not move the kit once the test starts. Write down the start time and location. When the test is done, seal it as directed and send it to the lab promptly so the result is valid.
Closed-House Conditions
Closed-house conditions mean keeping windows and doors closed, except for normal coming and going, for at least twelve hours before the test and for the whole test period. This gives a fair picture of radon in the home.
Keep the heating or air conditioning running as you normally would. Avoid running whole house fans or window fans that pull in outside air. Do not open windows to air out the house during the test.
If the result is well below the action level, file it with your install paperwork. If it is not, the contractor should check suction, look for open sumps, drains, or cracks, and confirm the fan is working before deciding on any change. Retest again after any adjustment.
A Fair Test Gives a True Answer
Getting the retest right gives you confidence that your radon system is doing its job. If you have questions about timing, placement, or a result that seems off, call us and we will connect you with a local contractor who can help sort out the next step for your York home.
Frequently Asked Questions
Can I use the same type of kit I used for the first test?
Yes. Using the same type of short-term kit makes it easier to compare before and after results. Follow the directions for the test length and mail it to the lab promptly. If your first test was long-term, a short-term retest still works for confirming the system.
Should the kit go near the radon pipe?
No. Place the kit in the general living area, away from the radon pipe, sump pit, exterior walls, and vents. The goal is to measure the air you breathe in the room, not the air near the system components. Feel free to ask follow-up questions once you have the written estimate.
How often should I retest after the first post-mitigation test?
Plan to retest every couple of years and after major changes like finishing the basement, replacing the heating system, or adding a room. Also retest if the gauge on the radon pipe changes or the fan sounds different. If you are unsure, mention it when you call so it is covered during the estimate.