The average indoor radon level is estimated to be about 1.3 pCi/L, and about 0.4 pCi/L of radon is normally found in the outside air. The U.S. Congress has set a long-term goal that indoor radon levels be no more than outdoor levels. While this goal is not yet technologically achievable in all cases, most homes today can be reduced to 2 pCi/L or below.
See A Citizen's Guide to Radon for additional information. Also check out the EPA Radon site.
Step 1. Take a short-term test. If your result is 4 pCi/L or higher take a follow-up test (Step 2) to be sure.
Step 2. Follow up with either a long-term test or a second short-term test:
Step 3. If you followed up with a long-term test: Fix your home if your long-term test result is 4 pCi/L or more. If you followed up with a second short-term test: The higher your short-term results, the more certain you can be that you should fix your home. Consider fixing your home if the average of your first and second test is 4 pCi/L or higher.
Back in 1999 I added an addition on my house. I forgot about the previous Radon problem I had with my 1833 Greek Revival house with it's dirt basement floor. In the 1980's I had put down plastic and poured concrete to eliminate the 16 pCi/L readings. In 2002 I ended up sealing the crack around the addition's floating basement slab, sealing the sump pit, and installing a radon fan. At the time I purchased a Safety Siron Radon Gas detector (model HS80002). My Long-Term reading has been around 2 pCi/L for years. Occasionally the Short-Term reading would approach 4 pCi/L. The readings always seem higher in the winter or when it rains hard. Since I have been building weatherstations and posting the data to the Internet , I thought it would be interesting to capture the radon information and try to correlate it.
I have been a fan of the Rabbit Semiconductor processors, but I decided to learn about what the Open Source Hardware Arduino could do. I thought trying to post the Short-Term/Long-Term radon readings from my old Radon Gas detector to the Internet would be a great project. I'm always looking for good projects to work with the Schools on.
On the HS80002 unit, the AC plug is integrated into the PCB. Since I didn't want to ruin the unit, I decided to take a brute force approach to hacking it. There is easy access to the 2 digit LED when you take the cover off. I was still able to find the data sheet for the LED! Using a scope, I was able to find the two digit strobe signals. Then by looking at the LED display and the strobe signal I was able to deduce segments A-G.
Digit Strobes Segment signal
Ground Wire Digit / Segment Pins
Pushing the Long-term/Short-term switch momentarily will toggle the display between Long-term and Short-term Radon readings. The LED display alternates between showing which mode is selected and the Radon reading. Initially I used clips to connect to the detector pins.
Arduino GND => Ground wire on top of board Arduino 2 => Digit 1 strobe Arduino 3 => Digit 2 strobe Arduino 4 => LED Segment A Arduino 5 => LED Segment B Arduino 6 => LED Segment C Arduino 7 => LED Segment D Arduino 8 => LED Segment E Arduino 9 => LED Segment F Arduino A0 => LED Segment G
The Arduino 1.0 Sample code for Safe Siren Radon Gas Detector Model HS80002 shows how it is relatively easy to create text with the radon value. This can then be used by a more complex Sketch to post the information to a data collection site like Pacube.com. Arduino 1.0 has several example sketches under File => Examples => Ethernet such as PachubeClientString.
I wanted to get another Safety Siren Radon detector so I could put one down in the basement and leave another one on the first floor where we spend most of our time in the house. When I went to purchase another Safety Siren Radon Detectors, I could only find a newer model (HS71512). There are several differences. The display now has four 7-segment LEDs and it reports in 0.1 pCi/L. The mode is now displayed with two LEDs.
I decided to add more functionality with the interface to the HS71512. I wanted to record both the long and short term Radon readings and I wanted to be able to control my Radon fan. Currently my fan runs 24x7x365 and draws around 120 watts. It keeps 0.75 WC Static Pressure according to my meter. I don't know how many CFM it is. Newer Radon fans that run 81 CFM at 1" WC Static Pressure say they take 60-95 watts. There is no safe level of Radon, but my long-term background reading stays around 2pCi/L. I want to run some experiments to see how much electricity I can save if I only turn on the fan when the radon readings are greater than my background level.
Arduino GND => GND Arduino A0 => Digit 4 strobe Arduino A1 => Digit 3 strobe Arduino A2 => Digit 2 strobe Arduino A3 => Digit 1 strobe Arduion A4 => Long Term Strobe Arduino A5 => Menu Button control Arduino 2 => LED Segment A Arduino 3 => LED Segment B Arduino 4 => LED Segment C Arduino 5 => LED Segment D Arduino 6 => LED Segment E Arduino 7 => LED Segment F Arduino 8 => LED Segment G Arduion 9 => Radon Fan Control
The transistor, diode, resister, and relay are used to "push" the menu button. Sparkfun has a nice discussion of how to use a relay. The Powerswitch Tail is used to control the radon ventilation fan. It draws it's power from the AC and only requires several ma at 5VDC to control.
Pachube ("patch-bay") connects people to devices, applications, and the Internet of Things. As a web-based service built to manage the world's real-time data, Pachube gives people the power to share, collaborate, and make use of information generated from the world around them.
This is a perfect repository for our Radon data. It provides a simple HTTP interface to post data and applications which generate charts that can be included on your web pages: