Thread: radon protocol - closed house conditions

I've heard differing opinions as to why there is a requirement for closed house conditions in short term radon testing.

Is the rule intended to cause the highest reading possible?

If so, then the conclusion is a closed house will have higher radon, correct?

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The protocol for short-term radon testing calls for closed-house conditions because the intent is to measure the home's potential for radon. With closed-house conditions the radon inside the house is not diluted by outside air. We want the house to be under closed-house conditions so we drive the radon levels as high as they will go and measure that level.

On the other hand, closed-house conditions are not required for long-term radon tests because LT radon tests are intended to measure radon levels the occupants are exposed to under normal lived-in conditions.

There are many factors that affect radon levels in a house. Usually opening windows and exterior doors will cause radon levels to drop because the indoor air is diluted by outside air (that usually contains much less radon). But it is not unusual for radon levels in a house to increase due to open windows. (An open window on the top floor of a house can cause more radon to be drawn into the basement due to stack effect.)

I wanted to get this reply posted before the thread is hijacked by the usual radon naysayers.

Bruce,

Thats exactly the way I remember it from the Kaplan Certi course in Radon Measurement I took to get my NRPP cert.

Come to think of it, I just realized you conduct that course in part.

The reason I asked is another inspector in my area (who I respect) said that opening windows and exchanging air in the lower level being tested would raise the radon by removing the older gases and allowing newer ones in. I thought it sounded strange since I had never heard it that way. Maybe he got that mixed up with the potential stack effect of opening the upper floor windows.

Originally Posted by Bruce Breedlove

The protocol for short-term radon testing calls for closed-house conditions because the “intent is to measure the home's potential for radon”. With closed-house conditions the radon inside the house is not diluted by outside air. “We want the house to be under closed-house conditions so we drive the radon levels as high as they will go” and measure that level.

These statements are not correct. The purpose of closed house conditions for a short term test is to measure the radon level at equilibrium – not to measure the homes potential and not to drive up the levels as high as they will go.

In order to understand the reason for closed house conditions and equilibrium we need to have a short discussion on the Uranium decay chain. Uranium 238 has a half life of 4 billion years. As it decays it changes properties. When Uranium fully decays (8 billion years) it becomes lead 210. Radon 222 is a decay product within this decay chain and it is a gas. It is the only gas in the Uranium 238 decay process.

Unlike Uranium, Radon (gas) has a half life of only 3.8 days. The decay products of Radon gas are Polonium 218 (3 minute half life) to Lead 214 (27 minute half life) to Bismuth 214 (20 minute half life) to Polonium 214 (u seconds half life) It is the Radon decay products (specifically Polonium 218 & 214) that are the major contributors to the health problem to humans. These products contribute most of the dangerous Alfa particles that destroy lung tissue. (20 times more dangerous than Radon gas)

The house is closed for 12 hours because equilibrium has been reached. - The amount of radon entering the house is equal to the amount of products decaying off, falling to the floor, and plating out on surfaces. It has stabilized

It drives me crazy when people say the house has been closed for 6 months – so they expect the radon to be higher. – Just not true. Radon and its decay products have a relatively short life and do not build up. They come in and go pretty fast, but will reach dynamic equilibrium in 12 hours, hence the reason for 12 hour closed house conditions.

Originally Posted by Ken Amelin

These statements are not correct.

. . .

It drives me crazy when people say the house has been closed for 6 months – so they expect the radon to be higher. – Just not true. Radon and its decay products have a relatively short life and do not build up. They come in and go pretty fast, but will reach dynamic equilibrium in 12 hours, hence the reason for 12 hour closed house conditions.

I did not mean to imply that radon levels continue to increase after equilibrium has been reached. Sorry for any confusion.

Radon is naturally occurring it comes from the decay of radio active materials like dirt and from granite rock; in many areas of the country they use crushed granite rock as fill under slabs or in crawl spaces. Seems sort of dumb to test for what God placed there naturally. I personally have done more than 2,000 short term tests and mitigated more than 300 homes in western North Carolina. Where the EPA says that 20,000 people die every year from Radon exposure I have never known any one to have scrummed from that fate. Have you? Still good folks from up north still come to ?Florida and ask if Radon Testing is necessary.

Closed house conditions for 12 hours is required for levels to come to equilibrium, testing must be done in the lowest level of the home or any potential potential living area.

HAPY NEW YEAR!

There are often multiple reasons behind some of the protocols.

Another reason for the closed-house protocol is to maintain as stable of an environment as possible. If the radon continuously jumps around every time the wind moves outside, the measurement devices will have one heck of a time keeping up with what is going on, especially since nearly none of the radon devices in use today use air pumps, meaning that it takes time for the radon to diffuse into the device. Closed house conditions slow the pace as which the indoor air can become diluted or even more concentrated, meaning that we can get a more reliable reading during the test.

I hope this helps. Happy New year!

Shawn Price