Radon 1027 Averaging Method

Simple question… perhaps.

If I conduct a test that is longer than 90 hours with a Sun Nuclear 1027 CRM, is the Overall Average on the printout the average of the 90 hourly data points or the average of the entire testing period? Also, when the AVG button is pressed at the end of the test, does this represent the overall AVG, or only the AVG of the first 90 hours?

After hearing some responses, I will explain the results of a recent test I performed which leads me to ask this question.


1027’s average the last 48 hours worth of data and begins to discard older data as new information is gathered. You can not get a 90 hour average with a 1027 device.

Are you sure about that Scott? I thought the averaging continued ongoing regardless of the time, but only the most recent 90 hours were stored for reporting. (And they do store and report up to 90 hours, that is a fact.)

The AVG button only gives you the last 12 hr average.

Here’s an interesting fact, and why I don’t publish my hourly values any longer…

Each hourly value is itself an average of 3 samples taken that hour. The value stored has multiple decimal places, but the value reported is rounded to one decimal place. When the final average, and EPA averages are calculated, the math is performed on the actual values (with all the extra decimals), and the result is then displayed rounded to one decimal. If you take the 40 hours reported and average them, you will almost never have the exact number reported by the machine. In other words, you are averaging “rounded” values, and the machine averages actual values.

Try explaining that to an irate seller when his average comes up to 3.8 when yours was 4.0. And he knows better because he’s an engineer. :roll:

Trust me when I say, if you are using a 1027, don’t put the hourly values in your report. Just give them the EPA average.

Interesting. I’ve always stated the date and time of testing on the report.

BTW I’m going to send my CRM (1027) out for calibration next week. Can anyone recommend a company for this service?

So Mark you are saying just give the average nothing else?

No. I have a 4 page report with recommendations and EPA information. I just don’t give the hourly values any longer unless I suspect tampering with the device. Then I do with an explanation as to why I suspect the device was tampered with.

Do you put 2 recorders in , Just asking. Here most only put one recorder in .

You’re right Mark. I just looked at the manual and the device does store 90 data points. Looks like I forgot that information. Apparently it’s time to take some refresher courses.

Just one. It’s a CRM. So it’s a good machine, and only one is required. It’s just that since it reports rounded averages for the hourly values, anal people try to figure their own final average (especially if it is close). Those don’t match the real rounded average because of the way the math works.

It raises more questions than it’s worth.

BTW, I use the hourly averages in my analysis of the test, and I keep them for my records. I just don’t give them to the client unless I suspect tampering, or the client specifically asks.

In NYS we have to be Licensed by ELAP to use a CRM. We are also reguired to give them the final EPA average including the uncertanty. We are also required to give them the hourly data if they ask for it.

We have used a monitor with a passive charcoal as a quality control test for thousands of tests; have had other monitors malfuntion and give false readings. (we used a femto tech monitor)

Having reports issued by Air Chek has made the radon reporting simple.
Copy of our report:

Does anyone have any good ideas on calculating the 12 hour closed house EPA protocol average. I wish the 1027 had this feature.

I add up each 12 hour readings and divide by 12. Then I add all the hours except for the first 12 to determine the 12 hour closed house condition.

Doing this on a 90 hour test would take a few more minutes.

I have never had a problem with explaining the hourly averages to a client or Realtor. I have had a few people ask why is there such a fluctuation from one hour to the next.

I do miss the Radalink Monitor for the humidity, temperature and pressure hourly readings. Made it easy to determine if the test was tampered with.

Maybe I will try a Sun 1029 one of these days.

The machine has two buttons to display levels on the LED: The button on the right labeled “CUR” gives you the current hours value. The button on the left labeled “AVG” give you the most recent 12 hour average.

In order to get the EPA Average (omitting the first 4 hours for equilibrium) you must download the data to the computer or print out a report.

I don’t have a problem explaining the hourly values, it’s the discrepancy between the actual average and the average of the printed values that I am avoiding. Since leaving that out of the report, I’ve not had a single negative comment or question about that. I don’t think that anyone has missed it. I’d be happy to give it if someone asked, they just never ask.

My opinion is why put stuff in a report, that doesn’t really tell the client anything new, and could potentially cause unnecessary problems or questions later.