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Radon mitigation monitoring for homes and buildings - This is a DIY project for the Raspberry Pi or similar system using an inexpensive Honeywell sensor with a couple of wires. The software is written in Python and runs under Linux.
According to the US Environmental Protection Agency (EPA), radon gas is the major cause of lung cancer amongst non-smokers killing about 21,000 people each year in the USA and 20,000 in the European Union. Radon gas is part of the breakdown chain of naturally occurring radioactive materials in the ground beneath our homes. It seeps into our homes through the tiniest of openings including tiny cracks in our basement floors, crawl spaces, and building foundations. It is invisible, odorless, colorless, and tasteless. Worse yet, it clings to dust and surfaces and is easily inhaled making it a severe health hazard. Scientists estimate that half the radiation we are exposed to in our lifetimes comes from radon gas. More than what we are exposed to from cosmic rays, medical / dental screening, food, and drink combined! When I recently bought a house I was told that radon was not an issue. I then bought a radon detector. It measured over 8 pCi/L whereas outdoor levels are typically only around 0.3 pCi/L. Urgent action was required! A review of mitigation systems offered alternatives from venting to active fan systems that either pressurize the whole house with outside air or under home depressurization (vacuum). The home already had an under concrete slab vent system so it was time to get an active fan system. The fan systems usually connect a sump well, drain tile, or sub-membrane beneath the building foundation or slab to a fan that then vacuums the vapors including radon gas to the outside where it disperses. The vent area should not be above or below a living area nor within 10 feet of windows, doors, or openings. I installed a radon fan for mitigation and the measured radon levels started to drop over the next few weeks from over 8 to under 1 pCi/L. Radon has a half-life of 3.8 days so it takes a while to dissipate. The levels are now running around the typical outdoor level. However, if the radon mitigation fan should ever fail, I would silently be exposed to very high levels of radioactive radon.
I installed a u-tube manometer to measure the suction of the radon mitigation fan system as shown in the figure. A manometer uses the difference in water height in a U-shaped tube to show the pressure difference. They are available for about $10 - $20 USD. However, most people don’t spend a lot of time in the basement or under their home in a crawl space looking at a manometer on their radon mitigation system. There are commercial alarm systems that are available for about $80 USD that sound an alarm if the radon mitigation system loses pressure. However, I noticed that when we have windy days, the wind gusts as seen on the manometer are large. I was looking for something that was better. I wanted something that I could adjust the alert levels and also something that wouldn’t sound an alarm in the middle of the night, which would be worse than a smoke detector’s low battery chirp in the middle of the night. I wanted a system that would send an alert to my cell phone as a text message that I could then quickly follow up on the next day.
Websites for further reading:
US EPA: Find Information About Local Radon Zones
US EPA: 2013 Consumers Guide to Radon Reduction
Minnesota Department of Health: Radon Mitigation
The Raspberry Pi looked like an ideal platform to monitor the radon mitigation pressure. This project uses a small inexpensive digital pressure sensor from Honeywell with a Raspberry Pi to monitor and send alerts for a radon mitigation fan loss of vacuum. The alerts can be an email or SMS message sent via email. Feel free to contribute with custom alert options such as MQTT, IFTT, etc. RadonMaster™ logs the pressure sensor readings to a Comma Separated Variable (CSV) file, MQTT, or InfluxDB so that the data can be plotted using MatPlobLib, in a spreadsheet, or any tool that supports MQTT or InfluxDB. The program is written in Python and can be ported to additional platforms, but the RPI is one of the most common platforms.
This program can connect to the AirThings WavePlus using the Raspberry Pi’s Bluetooth. The program will include the WavePlus sensor data in the radonMaster™ status message (daily, weekly, or monthly) and send an alert when one of the sensors changes outside of brackets defined in the thresholds of “wave.py” or custom alerts. The default thresholds were set to be similar to recommendations at the end of 2020. The program will read and log all of the sensors from the WavePlus which include:
- Radon short-term average
- Radon long-term average
- Volatile Organ Compounds (VOC) levels
- Carbon Dioxide (CO2) levels
- Temperature
- Relative humidity
- Atmospheric air pressure
The program runs from a terminal window or at boot. If run from a terminal window the status screen is as shown below:
Fri, 02 Apr 2021, 15:15:00 Vacuum: 0.82 in.wc
Fri, 02 Apr 2021 15:15:32
Radon ST avg: 0.5 pCi/L Green
Radon LT avg: 0.6 pCi/L
VOC level : 84.0 ppb Green
CO2 level : 457.0 ppm Normal
Temperature : 61.1 degF Blue
Humidity : 29.5 %rH Yellow
Pressure : 29.35 inHg
radonMasterPlot.py plots the radon mitigation fan pressure log and the WavePlus log data. You can view the plots and pan/zoom to specific time periods for the measurements. It uses MatPlotLib and is easy to customize to plot what is of interest to you. Figure 1a is an example plot.
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- Honeywell ABPDRRV001PDSA3 or ABPMRRV060MG2A3 pressure sensor available from Mouser, Arrow, Newark, Digikey, etc. for around $13 USD Mouser: ABPDRRV001PDSA3
- Plastic tube 1.6mm ID Amazon: Plastic Tube
- Wire, soldering iron, and solder
I used the ABPDRRV001PDSA3 which is a 3-wire SPI bus interface in a DIP package (Dual-Inline Package used with breadboards). I have also used the ABPMRR060MG2A3 which is a 2-wire I2C bus interface but in a surface mount package which requires soldering. Both are 3.3 Vdc supply voltage. The I2C pull up resistors are not required when used with the RPI.
- Raspberry Pi (any of the following)
- Power adapter for your Raspberry Pi
- Heatsinks (optional)
- SD-Card
For installing the Raspberry Pi operating system, you may want a USB keyboard and USB mouse along with an HDMI cable and monitor. If using the RPI4, a Micro-HDMI to HDMI adapter may be needed. It is possible to install the operating system without a keyboard, mouse, and monitor, but simpler is sometimes better. Once installed and configured you may want to switch to SSH or remote desktop so that you can remove the monitor, mouse, and keyboard.
A professionally installed Radon Mitigation system can cost around $2,000 USD or more. I installed mine for several hundred dollars in an afternoon and had excellent results. The Airthings Wave Plus radon monitor is outstanding. Here is what I purchased for radon detection and mitigation:
- Radon monitor: Airthings Wave Plus
- Radon Mitigation Fan Options
- RadonAway RP145 Radon Mitigation Fan
- RadonAway RP140 Radon Mitigation Fan Slightly less air flow but more energy efficient than RP145
- RadonAway 50018 Easy Read Manometer
- 3” to 4” Couplers depending on pipe size you plan to use from the sump well
- Butyl tape to seal sump well Many people are recommending various silicon sealants which are messy and difficult to remove. An alternative is Butyl tape since it is easy to remove to service the sump pump and backup pumps inside the sump well.
Each Honeywell pressure sensor is either i2c or SPI, but not both. The ABPDRRV001PDSA3 which is a 3-wire SPI bus interface is recommended as it is a DIP package.
RASPBERRY PI SPI PINS to ABP PRESSURE SENSOR (5-wires total):
| RPI 40-pin | SPI ABP (From Table 8 in Honeywell Data Sheet) |
|---|---|
| Pin 17 (+3.3 VDC) = | Pin 2 (+3.3 Vsupply) |
| Pin 21 (SPI_MISO) = | Pin 5 (MISO) |
| Pin 23 (SPI_CLK) = | Pin 6 (SCLK) |
| Pin 24 (SPI_CE0_N) = | Pin 3 (SS) |
| Pin 25 (GND) = | Pin 1 (GND) |
RASPBERRY PI PINS to ABP I2C PRESSURE SENSOR (4-wires total):
| RPI 40-pin | I2C ABP (From Table 8 in Honeywell Data Sheet) |
|---|---|
| Pin 1 (+3.3 VDC) = | Pin 2 (Vsupply) |
| Pin 3 (SDA1) = | Pin 5 (SDA) |
| Pin 5 (SCL1) = | Pin 6 (SCL) |
| Pin 6 (GND) = | Pin 1 (GND) |
The 3.3 VDC pressure sensors are recommended but, if you purchased a 5.0 VDC pressure sensor then the 5 VDC supply on the pressure sensor pin 2 would go to the RPI Pin 2 (+5.0 VDC). You will need to convert the ABP’s 5 volt bus signals to the RPI bus 3.3 volt levels so this is not as straight forward as using the 3.3 VDC pressure sensor.
You will purchase either an SPI or I2C pressure sensor, not both. The SPI version is recommended but both sets of photos are included to provide choices.
Figure 2: SPI Pressure Sensor
Figure 3: SPI Wiring on RPI
Figure 4: Alternative I2C Pressure Sensor Power Pins
Figure 5: Alternative Pressure Sensor I2C Bus
Figure 6: Alternative I2C Wiring on RPI
Here is an example of an existing manometer that was installed on the mitigation pipe. You can replace the manometer tube with a tube that runs to the Honeywell pressure sensor port P1 (shown in photo) or you can drill a new hole that fits the tube size.
Figure 7: Tube Installation
Here are the instructions to install the Raspberry Pi Operating System. Raspberry Software Install Procedure
Before continuing make sure your operating system has been updated with the latest updates.
sudo apt-get update
sudo apt-get upgrade
sudo reboot now
If using a Honeywell I2C pressure sensor you will need this library. I would recommend installing it as you may want to use I2C in this project or others. If you don’t install python3-smbus, you will need to comment out the appropriate lines in the program code.
sudo apt-get install python3-smbus
sudo raspi-config
Under interface options, enable either or both the SPI and I2C interfaces depending on the Honeywell ABP pressure sensor that you purchased. In general it is better to enable both so that the interfaces are available for use with projects. To verify i2c operation, if you have an i2c Honeywell pressure sensor type the following command which should result in the i2c device address 0x28 being displayed:
sudo i2cdetect –y 1
To verify SPI operation, type the following command which should result in the SPI bus being listed:
ls /dev/*spi*
There are 4 python files: radonMaster, sensorHnyAbp, sendEmail, and cfgData. To get a copy of the source files type in the following git command assuming you have already installed git:
git clone https://github.com/BrucesHobbies/radonMaster
If you desire, you may edit radonMaster.py and change the user configuration section at the beginning of the file.
Edit the RadonMaster.py program file if you used a different sensor than the ABPDRRV001PDSA3. Please change the statement to match the variable range, units, and output type of the sensor you purchased. For example if you purchased the ABPMRRV060MG2A3 change from “001PDS” to “060MG2”. Again, this statement is in the radonMaster.py file. More complete details are found in “sensorHnyAbp.py”.
sensor = sensorHnyAbp.SensorHnyAbp("001PDS")
To disable alert messages, change the alertsEnabled value to 0 in “radonMaster.py”.
alertsEnabled = 1 # non zero enables sending of email messages
You can use Google Gmail to send status and alert emails. Others have also used Microsoft Live/Outlook/Hotmail, Yahoo, Comcast, ATT, Verizon, and other email servers. Currently, status and alert messages are sent by email which can also be sent as an SMS text to your cell phone. Gmail works with Python on the Raspberry Pi if you set the Gmail security settings to low. As such, you can create a separate Gmail account to send messages from. Under your Gmail account settings you will need to make the following change to allow “Less secure app access”.
Then click on “Turn on access (not recommended)” by moving the slider to ON. Then click the back arrow.
When your first email is sent at program startup, Google will ask you to confirm that it is you. You will need to sign into the device email account that you created and go to the critical security email that Google sent you and confirm you originated the email before Google will allow emails to be sent from your Python program.
Once you have created an account, start the radonMaster™ program. Type:
python3 radonMaster.py
The first time the program starts up it will ask you for your gmail user id and password for the account that you just created to work with this program. The password will be saved to a file called cfgData.json. Please be careful to not send that file to others. If you ever change your password you will need to delete cfgData.json so that the program will ask you for your password again.
Enter sender’s device email userid (sending_userid@gmail.com):
sending_userid@gmail.com
Enter password:
password
Next the program will ask you for the recipient email address. This can either be the same email address, your primary email address or your SMS cell number carrier’s gateway. To email an SMS to your cell phone construct the recipient email depending on your cell phone carrier:
| Carrier | Format |
|---|---|
| AT&T | number@txt.att.net |
| Verizon | number@vtext.com |
| Sprint PCS | number@messaging.sprintpcs.com |
| T-Mobile | number@tmomail.net |
| VirginMobile | number@vmobl.com |
Enter recipient’s device email userid (receiving_userid@something.com):
Receiving_userid@something.com
If alerts are enabled (alertsEnabled=1) and you have entered valid email information you can choose to have a status message sent for a RPI well-being check. To change the time of day for the status message from noon local time, edit the hour and minute. Entering values outside the expected values will allow you to disable status messages. Range for HH is 0 -23 and for MM is 0 – 59.
statusMsgHHMM = [12, 0] # Status message time to send [hh, mm]
Status messages are sent in one of three ways: fixed interval in days, on a specific day of month, or specific day of the week.
# Interval in days
# (0=use DOW, else 1=every day, 2=every other day, 7=weekly, etc.)
statusInterval = 1
# Day of month if non-zero, 1=first day of month, up to 28, or 30 some # months.
statusDOM = 0
# Day of week if interval and DOM are not used (0=Mon, 1=Tue, etc)
statusDOW = 0
If alerts are enabled, you can choose to throttle the alerts. The interval can be as short or long as you like. Default is 3600 seconds which is one hour.
# Wait this long before sending another email - seconds
minIntervalBtwAlerts = 3600
Please feel free to fork and contribute or provide feedback on priorities and features. The file pubScribe.py provides the ability to configure data logging, status, and alerts. Selection of options is done in pubScribe.py by uncommenting the ENABLE lines.
- Comma Separated Variable (CSV): supported
- Email: supported
- Relay / buzzer
- MQTT: supported
- OpenHab
- Home Assistant
- Domoticz
- InfluxDB: supported
- IFTT
- PubNub
- Twilio
- Cellular
- APRS
On the first time RadonMaster™ program starts, it will ask you for your email userid and password for the email account that you created to use for the alerts and status messages. Once you have entered a password the program will send an email message indicating the program has started up.
RadonMaster™ will then display the first reading from the pressure sensor including status and temperature according to the type of sensor you selected.
RadonMaster™ will then establish a baseline vacuum as measured by the sensor. Let it complete the calibration. To then test the alert feature, partially remove the tube from the pipe. An alert should be generated. Reinsert the tube into the pipe. Averaged readings should return to normal.
To test the status feature, wait for the status time and verify that you received a status message.
While not required or recommended, you can change the following configuration parameters. # time interval in seconds between fan vacuum measurements # (default: 1, possible values: 1, 2, 3, 4, 5, 6, 10, 15, 20, and 30). tInterval = 1
# Wind gusts averaging time in measurements,
# recommend multiple measurements due to wind gusts and
# water sloshing in sump well
tAverage = 60
# --- Fan speed alert settings ---
# Be sure and account for variations for wind
# gust effects on vent opening and sump pumping
pDeltaLowSide = 0.4 # delta inches water column
pDeltaHighSide = 0.4 # delta inches water column
pLowPressAlert = 0.5 # Abs value in case auto calibration is off
If you will be connecting to the AirThings WavePlus using Bluetooth on the RPI, you will not need to install any hardware, but you will need to install the “bluepy” library.
sudo pip3 install bluepy
Once the library is installed verify that Bluetooth is powered on using the “show” command from bluetoothctl.
sudo bluetootctl
[bluetooth]# power on
[bluetooth]# show
[bluetooth]# exit
Verify that bluetooth is powered on. If the library fails to install or Bluetooth fails to power up, radonMaster.py should recognize that and will continue to read the Honeywell pressure sensor for the radon mitigation fan vacuum. By default, reading the Airthings WavePlus is set off. See more about this under “Configuration of alert monitor and logger for Airthings WavePlus”.
To enable logging and monitoring and logging of an Airthings Wave Plus change the following variable in radonMaster.py to the following:
AIRTHINGS = 1 # Default = 0, which is monitoring and logging disabled
For Bluetooth, “radonMaster.py” will need to run as super user (sudo) to have sufficient privileges to access the bluetooth hardware.
sudo python3 radonMaster.py
radonMaster reads the WavePlus every 15 minutes but the WavePlus updates the radon measurements once an hour so the radon measurements will be unchanged while the temperature, humidity, and other sensors update more frequently. It is normal to lose a few measurements a day due to radio interference or collision with a smart phone app reading the WavePlus.
radonMaster.py will find any WavePlus sensors within Bluetooth range. The program assumes only a single WavePlus. If there are more than one WavePlus, comment out the find_wave function and type in the serial number found on the back of the WavePlus. Inside “wave.py” are a number of variables that can be changed. It is recommended to leave them at their default values.
#
# Airthings updated notification brackets
#
radonBrackets = ((4.0,"Red"),(2.7,"Yellow"),(0.0,"Green"))
vocBrackets = ((2000.0,"Red"),(250.0,"Yellow"),(0.0,"Green"))
co2Brackets = ((2000.0,"Red"),(800.0,"Yellow"),(250.0,"Poor"),(0.0,"Good"))
#humidityBrackets are a separate function
tempBrackets = ((77.0,"Red"),(64.0,"Green"),(-99.9,"Blue"))
THROTTLE_TIME = 24*60*60 # seconds
Simply open a new terminal window. Switch to the directory.
python3 radonMasterPlot.py
Use the buttons on the bottom of the plot windows to zoom and pan to the specific months, weeks, days, or hours of interest.
Type the following command:
sudo crontab –e
Select the type of editor you are familiar with. I used nano. Add the following line at the end of the file and then press ctrl+O to write the file and ctrl+X to exit the nano editor.
@reboot sleep 60 && cd radonMaster && python3 radonMaster.py
Let us know what you think of this project and any suggestions for improvements. Feel free to contribute to this open source project.