Instrumentation & Measurement Magazine 26-4 - 22

measurement
andapplications continued
upload them to a storage
cloud service and from it
to a web app.
Fig. 2. Radon concentration distributed measurement architecture.
or taste. Its more stable isotope, radon-222, degrades over
a short period of time, emitting alpha-type ionizing radiation.
Despite the short lifespan, radon is a common element
on the earth due to the widespread presence of Uranium and
Thorium. Radon concentration in the atmosphere is scarce,
but, thanks to several carriers like water or CO2
, higher concentrations
could be found and then measured in closed
environments. The International Agency for Research on
Cancer (IARC) categorized radon and its decay products as
carcinogenic agents to humans in 2012. Research outcomes
have shown that continuous indoor exposure to radon concentrations
of more than 100 Bq/m3
(Becquerel/cubic meter)
increases the risk of developing lung cancer [25]. The EU
Member States are required to develop a national radon
action plan that addresses long-term risks from radon exposures
in dwellings, public buildings, and workplaces for
any source of radon, whether from the soil, building materials,
or water. To address this directive, many EU Member
States issued more stringent national radon plans and regulations,
requiring an annual average radon gas concentration
of 200 Bq/m3
or lower for new construction. Researchers
are looking into developing sensors and sensor networks
that determine the amount of radon gas in interior environments
and workplaces [26], [27]. Following such a trend, an
IoT platform, specifically designed for monitoring radon gas
concentrations in indoor settings, is described in [28]. The
communication infrastructure is based on the MQ Telemetry
Transport (MQTT) protocol, which is popular in IoT systems.
It is used to periodically gather measurements of temperature,
relative humidity, and radon gas concentrations and
22
As shown in Fig. 2,
the system architecture is
based on three main components:
the sensor nodes
measure all of the required
physical quantities; the
MQTT broker manages
messages from the sensors
nodes and addresses the
captured values to the storing
application; and lastly,
each measured value is
saved into a database easily
viewable from the custom
web app. In this particular
application, the sensor
nodes include four sensors:
a radon sensor, which
measures the alpha decay
particles of both Radon-222 and its progeny with a time resolution
of 10 minutes; a couple of temperature and humidity
sensors, which are used to correct the measured radon value
since those factors affect the radon sensor; and a pressure
sensor.
The architecture is designed to be extremely flexible; each
sensor node could be different in terms of installed sensors. As
an example, a battery-powered sensor node could send also
the battery state of charge; instead, that information is not useful
for a grid-powered sensor node.
The cloud database server includes a small application that
relates to all topics managed by the MQTT broker and sends all
the measurements to the database tables. The web application
contains a publicly, remotely accessible main page for any user,
in which there is a map where the installed sensor nodes are located
by their coordinates (longitude/latitude). Each sensor
node has a photo that shows the measurement plant and, on
another page, all the collected measures for that node.
In conclusion, the MQTT protocol is used to enable the visualization
of the measurements between the sensor nodes
and the final user, with also the possibility to store all the measured
values in a MySQL database. Since the measurement
data are constantly transmitted to the database, it is possible, in
every moment, from all over the world, to see the most recent
measurements using the web application. Extensive adoption
of radon sensors, especially in workplaces, could increase
the air quality significantly and in general, improve workers'
safety. To this aim, new types of sensing nodes could include
other sensors for monitoring not only the radon concentration
but also the CO2
concentration or the light flickering.
IEEE Instrumentation & Measurement Magazine
June 2023
Instrumentation & Measurement Magazine 26-4

Table of Contents for the Digital Edition of Instrumentation & Measurement Magazine 26-4
