Radon on the Front Range, and what a test actually tells you

The concentration of radon in the air inside the house, over a period of time, in picocuries per liter. The EPA sets an action level and recommends fixing a home at or above it, and also notes that there is no level considered risk-free. Both halves of that matter: an action level is a threshold for acting, not a line between safe and unsafe.

Most real estate transactions use a short-term test, typically placed for a couple of days under closed-house conditions. That is a snapshot, which is the compromise a contract timeline forces. Long-term tests over ninety days or more give a better picture of what a household actually breathes, and are the right instrument once you own the place.

Levels vary with season, weather, and how the house is being run. A closed-up house in winter commonly reads higher than the same house with windows open in July. That is not the test being unreliable, it is the concentration genuinely changing.

Radon testing sits inside the inspection period like any other investigation, and the deadline is the constraint. A short-term test needs the house closed up for a period beforehand and then the duration of the test itself, so it has to be ordered early in the window rather than at the end of it.

Colorado’s standard contract addresses radon among the matters a buyer may investigate, and the seller’s property disclosure asks about prior tests and any existing mitigation system. Both are worth reading rather than skimming: a previous test result, or an installed system, changes what you are asking for.

If a result comes back elevated, the usual outcomes are that the seller installs a system, credits the buyer to install one, or the parties split it. It is one of the more routinely resolved objections in Colorado residential practice, which is worth knowing before the number frightens anybody.

The standard approach is active soil depressurization: a pipe drawing air from beneath the slab or from the crawl space, and a fan moving it above the roofline so it disperses outside rather than entering the house. It runs continuously and uses a modest amount of electricity.

It is a day’s work in most houses, and it is visible afterwards, which some sellers dislike. Weigh that against the alternative, which is an unmitigated house and a disclosure obligation.

Test again after installation. A system is a mechanism, not a guarantee, and the point of the exercise was a number rather than a pipe. Colorado licenses radon professionals through the Department of Regulatory Agencies, so verify that whoever measures or mitigates holds the current credential.

Radon can also be dissolved in groundwater and released indoors when that water is agitated, in showers and washing machines. On a public supply this is generally handled before the water reaches you. On a private well it is not, because nobody is treating it but you.

It is a separate test from the air test and it is not part of a standard well panel, which is usually looking at bacteria, nitrates and similar. If you are buying acreage on a well, ask specifically rather than assuming the water testing covered it.

This is the one place where the metro answer and the acreage answer genuinely differ, and it is the reason this guide is not filed as a purely suburban concern.

Knowing the number before you list is worth more than not knowing it. A pre-listing test costs very little and turns a possible renegotiation into either a non-issue or a job you scheduled at your own pace with your own contractor.

If a system is already installed, have the paperwork ready: who installed it, when, and the post-installation test. A mitigation system with documentation is a resolved item. The same system with no records invites a buyer to re-open the question from the start.