Measurement Performance of Electronic Radon Monitors

Round 1

Reviewer 1 Report

Comments and Suggestions for Authors

The manuscript reports the performance comparison between various electronic radon monitors and gives an analysis on each device. The topic of the manuscript was very interesting for publication. However, there are revisions and questions to improve the manuscript before it can be published. 

The manuscript is too long and should be written more concisely, especially in the methodology section. 

The statistical analysis and metrological characteristics were given too detailed explanations, it should be written more concisely, and a general description of the method followed by relevant references should be sufficient.

The manufacturer's responses were given in the supplementary material; however, these responses have not been incorporated into the manuscript.

 

The humidity of “the standard test condition” was very low considering commonly found average humidity in the environment. The definition of standard test condition should be given a relevant argument/description.

 

Author Response

Please find the responses of the authors in the attached file.

Author Response File: Author Response.docx

Reviewer 2 Report

Comments and Suggestions for Authors

This manuscript presents a test method and the results of measurements by comparison of a few radon detectors. The manuscript is mainly a technical description of these tests in different conditions. The equipment is characterized in terms of performance and purchase price. The authors present a test activity under several simulated conditions to determine the performance of "14 different types of devices from 9 manufacturers". In conclusion, it was determined that some of them should be calibrated before being put on the market. This paper may be valuable for publication in this journal after revision.

 

Comments

In general, an article is important if other authors cite it. In its current form, several aspects do not make it attractive. The tests are based on equipment considered a reference. Their value can be considered within a project where some radon-measuring detectors must be selected, but it is limited in generality.

The structure of the test equipment is similar to that of ‘Recent Progress in Radon Metrology at IFIN-HH, Romania’ (https://www.mdpi.com/2073-4433/13/3/363, it is not in the bibliography). And in this case, a reference equipment of type Alpha Guard (DF2000) is used, but the topic is of interest: the implementation of a "Calibration Laboratory for installations measuring the radon activity concentration in air". Also, the usefulness of the test action is the compliance with the European Council Directive directive no. 2013/59/EURATOM. I think that the mention of this directive motivates more the realization of these tests which would be useful in general. Also, compared to the previously mentioned article, there are no pictures of the equipment used, a block diagram showing the basic elements described in the text. In its current form, each reader should imagine how the tests would be done, and where Alpha GUARD is positioned concerning the test device. The lack of a block diagram makes it difficult to read the article, which already has many tables that are hard to follow because they are on several pages.

Mainly in the article, the authors want to test the performances of some commercial equipment compared to one considered as a reference without mentioning the catalog data of the tested devices and distinguishing by price. Practically, the declared parameters of the device are important when you buy something. The tests should answer the question: are the technical data specified by the manufacturer correct? You look at that information when you make a selection and then at the price in the case of equipment that measures radon, then you make the choice. If you want something cheap, you can't neglect the performance because a big error can lead to erroneous information (for example values ​​over 5000 Bq/m³) that reaches the competent authorities and that can take radical measures in conditions where this is not the case. Also, one device can be cheap compared to another even though they are made similarly only because the expensive one is also accompanied by a quality certificate with calibration verification measurements, maybe a transfer function, the specification of a sensitivity that differs for each copy, etc. All these specifications cost and determine a higher price. So the price is not a good criterion and maybe it shouldn't be mentioned, it can contain many things depending on the merchant (an extended warranty, commissions, and the specifics of the local market for example).

Reading this article, you ask yourself who is it useful for? It is obvious the effort made by the authors and not only (probably there was also technical staff, facilities used, time, etc.). It should be specified if the tests are done with accredited metrological equipment (rows 57 - 59), the pressure, temperature, and humidity conditions do not refer to the catalog sheets of the equipment (useful information from the tests would be to mention if they do not correspond to the IEC 61577-2 standard, in which case I do not think they can be put up for sale). I currently use several types of radon detectors, some of which are included in these tests. An important parameter is the measurement time (exposure) which can vary from 5 minutes (large errors) to 4 hours (small errors). The relationship between data acquisition time (sample rate) and their error is very important and I have not seen it analyzed.

In practice, the tests must verify compliance and provide data for the calibration of the device being tested. Only the manufacturer or a trained staff can intervene in its device, otherwise the warranty is lost. In the case of applying the EU directive, we are talking about hundreds of pieces of equipment installed in basements, public places, etc. over a large area. In this case, it would be useful if the test resulted in some coefficients, and some tables - correction curves that could be applied to the measured data without interfering with them (maybe it's not even possible). I did not find an example of equipment that measures radon and has a self-calibration procedure or calibration by the user. The simplest is to apply a correction method to the measured data based on a calibration report made by an installation such as that of the BfS. I didn't find such a concern in the article but it can be done.

In the rows 94 – 99 area, a reference could also be included to the user interface facilities that can be on the device (display, buttons) and on a computer, tablet, etc. Software elements are important when choosing to buy a piece of equipment. If the data is saved in a format that forces you to buy software to be able to use it, the price of the device increases indirectly.

The authors allocated a few pages for chapter '2.4. Analysis of Measurements'. This could be useful by citing some calculation relationships but these are also general (there are no references, if it is an original approach it should be specified). What would have been interesting and useful refers to the measurement error depending on the sample rate which can usually vary from 5 minutes to 4 hours. Now, I work with a device that can provide you with data per minute, but internally, the data acquisition is made at one-hour intervals. There are equipment that have a pump for air absorption, others do not. This makes it possible to use a shorter acquisition period while keeping the determination error, which leads to the possibility of performing a mapping on the ground in a shorter time (for example 5 minutes in the case of the existence of an air pump, i.e. RTM 1688-2, is equivalent to 3 hours if this is missing, i.e. Radon Scout P)? Depending on the radon concentration, the data acquisition period is also adjusted by the operator to obtain an optimal error. I would have liked these things to be in the article because they are useful to those who measure in the field. Table 5 and Table 6 are hard to read, another form should be found or reduced. A reference to the product catalog sheet would have been useful (is it compliant or not, is there a solution to optimize the determinations?).

In rows 687 – 688 a reference is made to long-use devices connected to an external power source that could damage the internal batteries. Generally, there is an electronic switch that disconnects the internal batteries when there is an external power source. If the external power is interrupted, it automatically switches to batteries, this facility being common to many equipment. The only problem would be the quality of the batteries, which can eliminate a liquid that affects until destruction of the components it touches. I think this mention is less relevant than the analysis of the user interface (hardware and software), which parameters can be changed if there is a preview of the data with the possibility of a preliminary analysis, the data format, the connection mode RS232C, USB, WiFi, etc.

In lines 696 - 698, the authors recommend that the equipment be checked by an approved calibration center before use. Here it should be mentioned as 'approved' by the manufacturer because specific devices and procedures are used. Can BfS 'calibrate' a Radon Scout Plus? It can certainly make a test report such as the one from https://www.sarad.de/cms/media/docs/testbericht/Test_Bowser_Morner.pdf (for the report to be relevant the SARAD company called Bowser Morner although it could do it) or recommend sending it to the manufacturer for verification. I think the name "accredited calibration verification center" is more correct because that is what it does. It would be useful if, based on the report given by such a center, a correction method could be applied to the data acquired by the equipment in the conditions in which they fit into the data sheet of the device (otherwise it is defective) and the improvement of the results is desired. In the case of other devices, the result of calibration by the manufacturer is the updating of a transfer function.

The conditions under which the tests were done have been correctly analyzed in the supplementary material by the equipment manufacturers.

 

 

Author Response

Please find the responses of the authors in the attached file.

Author Response File: Author Response.docx

Reviewer 3 Report

Comments and Suggestions for Authors

In my opinion, the topic of the paper is very interesting. However, I am unclear on what the authors mean by standard test conditions'. Also, it is widely known that achieving such low humidity levels (<10%) in a typical home environment is very difficult and could not be possible. For measuring the background, I believe that 150 hours is sufficient. Why did the authors extend the period to 1000 hours? or Is it dependent on each instrument specification? Moreover, the authors used just two data points (upper and lower) for the linearity test; it is not sufficient to assess the linearity of the results. Based on author results, I think it should mention that the price also plays a significant role in determining the quality of devices, which differs from the author's conclusion.

Author Response

Please find the responses of the authors in the attached file.

Author Response File: Author Response.docx

Round 2

Reviewer 1 Report

Comments and Suggestions for Authors

The manuscript has been revised properly.

It can be accepted for publication under the current form.

Reviewer 2 Report

Comments and Suggestions for Authors

In the revised form, the article is much clearer and useful to those active in this field.

Reviewer 3 Report

Comments and Suggestions for Authors

Well revision the manuscript.