Radon Testing in Denver, CO

Why a Curve Beats a Number

A charcoal kit mailed to a lab gives you one figure averaged across the whole exposure. A continuous monitor gives you a reading every hour, and the difference matters more than it sounds. Houses do not sit at one level. A Denver basement can run at 2 through a mild afternoon and climb past 10 overnight when the furnace cycles and the stack effect pulls hardest. Both houses average out somewhere in the middle, and only one of them is telling you that people are sleeping down there through the peak.

Closed-House Conditions Are Not a Formality

Radon concentration is a ventilation story as much as a geology one. Twelve hours before the monitor starts, and for the whole 48 hours after, exterior doors and windows stay shut apart from normal coming and going. Whole-house fans and window air conditioning stay off. Skip that and the number you get describes a house nobody actually lives in — usually a flatteringly low one, which is the worst possible direction to be wrong in. Every result we issue states the conditions it was measured under, because a reading without them is not really a result.

Placement: the Lowest Level Somebody Uses

The monitor goes in the lowest level of the house that is lived in, or could reasonably be finished and lived in. In most of the metro that is the basement. In a Wheat Ridge ranch over a bare crawlspace it is the main floor, because nobody is ever going to put a bed in an eighteen-inch crawl. In a split-level it is the lower family room rather than the crawl beneath it — and split-levels are where this decision gets made wrong most often, because there are two defensible answers and they produce different numbers. Placement is also kept away from exterior doors, drafts, and anything that heats or cools the air around it.

Season, and What a Borderline Result Means

Readings along the Front Range are generally highest between November and March, when houses are sealed and the temperature difference driving the stack effect is largest. A summer test is still real data — it is simply data from the easy end of the year. If a July result lands near the action level, that is a strong argument for a winter follow-up rather than a clean bill of health. A long-term test running ninety days or more gives you a better picture of the annual average, and it is the better choice if you are staying in the house rather than closing on it.

What Happens After the Result

If the number is low, we say so and that is the end of it. If it is high, the same visit tells us most of what we need to price a mitigation system — the foundation type, the pipe routes available, whether there is a sump pit already open to the soil. If you are working to a transaction deadline, say so before booking, because testing inside an inspection window is scheduled differently.

How long does it take? Forty-eight hours of measurement, plus the twelve hours of closed-house conditions before it starts. Placement takes about fifteen minutes and pickup about the same.

Questions People Ask First