Thread: Radon: Is an 18.4 reading bad?

I am using the ProSeries 3 Radon detector by Family Safety Products and just did an inspection where, after 48 hours the reading was 18.4. To compare, my own basement read 22.4.

Since the device display range goes from 0.0 to 999.9, I'm not sure I'm interpreting this reading correctly.

Has anyone used this detector and can anyone help me figure out if I need to sound a warning to my client?

Thanks,

Mitch

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If the reading is pCi/L then 4.0 is the allowable level according to the EPA. Your meter must be reading in another unit or you have really high radon levels or you need to move a decimal point.

FLYGUY

i use these detectors. you should always test with two detectors using this device. when results are in. average the two devices as you would using e-perm devices. remember these devices have to be calibrated once a year.

have you had proper radon training?? doesn't sound like it-- because anyone who has would have known that answer. you can not just go and test radon if you are not certified. i recommend you use e-perm devices and let the labs determine readings until you are certified.

hey what else do you do without certification.

cvf

18.4 is high. Tell them the EPA action level is 4.0. Tell them to hire a qualified radon mitigation contractor.

Originally Posted by flyguy26

I am using the ProSeries 3 Radon detector by Family Safety Products and just did an inspection where, after 48 hours the reading was 18.4. To compare, my own basement read 22.4.

Since the device display range goes from 0.0 to 999.9, I'm not sure I'm interpreting this reading correctly.

Has anyone used this detector and can anyone help me figure out if I need to sound a warning to my client?

Originally Posted by CHARLIE VAN FLEET

have you had proper radon training?? doesn't sound like it-- because anyone who has would have known that answer. you can not just go and test radon if you are not certified. i recommend you use e-perm devices and let the labs determine readings until you are certified.

hey what else do you do without certification.

I'm with Charlie. If you don't know how to use your devices you should not be doing paid radon testing for clients.

Like Charlie, it sounds to me like you have not had proper radon training. While certification is not a necessity (if many states, e.g., Colorado) you really should take a good radon measurement course before you hold yourself out as a radon professional.

Is the ProSeries 3 Radon Monitor EPA an approved radon device? I have seen these devices and they are not all bad but I think they are better suited for home use rather than use by a radon measurement professional. Like Charlier said, radon devices should be calibrated yearly and the cost of calibration may exceed the cost of the device.

To answer your original question - "Radon: Is an 18.4 reading bad?" - the answer is, "Yes, it the units are pCi/L." But you would know that if you had proper training.

Originally Posted by flyguy26

I am using the ProSeries 3 Radon detector by Family Safety Products and just did an inspection where, after 48 hours the reading was 18.4. To compare, my own basement read 22.4.

Since the device display range goes from 0.0 to 999.9, I'm not sure I'm interpreting this reading correctly.

Has anyone used this detector and can anyone help me figure out if I need to sound a warning to my client?

Thanks,

Mitch

Isn't this a detector that is designed for a homeowner to keep plugged in all the time?

Mitch as other have said, you need to get some training. I would also look at investing in a CRM that is approved for use. You want a device that will provide you with an hourly reading, this way you can see spikes in the readings and more.

SCOTT

the pro series is approved by EPA and there is a home edition. only thing bad about this device is it cost $120--and to calibrate it cost $75. a year.
it compares with the eperm devices and is just as accurate.

cvf

The product site says this unit is for use only after a professional evalutation has been done, and its purpose is to monitor not evaluate radon levels. Yes a reading of 18.4 with this unit could be considered bad since it reads out in pCi/L.

Thanks to those of you who provided helpful information. I know that anything over 4 pCi/L is cause for concern. I was mainly asking if anyone had any experience with these particular detectors and whether they have experienced any anomalies with them since the alarm didn't go off.

Having said that, I don't appreciate the snotty comment from Charlie. While everyone may not be blessed with the scope and depth of Charlie's obvious intellect, there are those who are equally worthy in the trade and do a respectable job for their customers. His condescension is both unwarranted and unwanted.

FLYGUY,
I think that Charlie only wrote what a bunch of us were thinking. Bruce and Scott pretty much told you the same thing.

Asking if those levels are bad indicated implied that you didn't know what the action level for radon is.
I agree, that if you have not had some training in radon testing, you should not be doing tests for your clients.

Well then, I guess I wasn't clear enough in my initial post. I know that 4 pCi/L is the threshold at which the EPA says radon should be mitigated - it's mentioned in just about every shred of literature having to do with radon, including the manual included with the device I was concerned with.

My question was geared more to the notion that there might be something wrong with the unit, since it was registering 18.4 and there was no alarm going off. Or, I thought maybe there could be a decimal point issue instead.
It seemed odd to me that, if 4.0 is the safe maximum espoused by the EPA that the device would go all the way to 999.9!

Where would you have to be for the unit to indicate 950 pCi/L?

I hope that makes my question clearer.

Probably those radon caves in Russia.

Start here Mitch.

National Radon Proficiency Program - Entry-Level Radon Measurement and Mitigation Courses

One of the great things about the education is being able to answer questions immediately and correctly when clients ask you. Believe me, they'll ask all kinds.

FLYGUY
i always read the manuel on devices i'm about to operate.so as to know what i'm doing- if you read the manuel for the pro series you will find that you can turn the alarm on and off. again training comes to mind. if you are not certified for radon testing AT LEAST READ THE DETECTOR MANUEL.

what's up guy.if you knew 4.o picos were the standard--why the question?

oh yeah reading the manuel .forgot
sorry to offend but i think a bad question for a home inspector.
just my take on training and charging a client

cvf

Originally Posted by flyguy26

It seemed odd to me that, if 4.0 is the safe maximum espoused by the EPA that the device would go all the way to 999.9!

Where would you have to be for the unit to indicate 950 pCi/L?

Nature has a way of completely disregarding manmade boundaries. Earthquakes, hurricanes and floods go where they want to. Why shouldn't radon levels exceed some manmade "limit"?

18.4 pCi/L is not especially unusual in my area. I have made measurements in houses above 120 pCi/L and I know other inspectors who have had measurements above 700 pCi/L. Nature knows no limits.

One house where I did a radon test had an old gold mine running from the basement back into Pikes Peak. All that separated the basement from the mine was a small vestibule and a door. I placed an E-PERM in the mine (just to satisfy my curiosity) and got a measurement of just under 150 pCi/L. The basement measured above 100 pCi/L without mitigation and just above 2.0 pCi/L with mitigation.

Why does your device measure radon as high as 999.9 pCi/L? Why not? Why should the manufacturer place a lower limit on the device if it is capable of 999.9 pCi/L? Most homeowners using the device will never see a reading of 999.9 pCi/L but an occasional few will. If the manufacturer had decided the device should not read higher than 18 pCi/L (or some other level) many homeowners would have no idea they were really being exposed to seriously high levels of radon.

FLYGUY,

A reading of 18.4 pCi/l is not unusual, especially in your area. The detector you used is a home monitor and should not be used for testing.

I'm not sure how you used it in a clients home, but the monitor will report on radon levels over both the short term and long term (depending on your setting). The short term takes the average over a seven day period, the long term takes the average over the total time it is plugged in.

If you didn't keep it in for seven days then you would not get an average reading, you get spike readings which are not representative of the average levels and are not in accordance with EPA protocol.

Here is the instruction manual for further reading
Pro Series 3 Digital Radon Gas Detector Instruction Manual

hey ken

ken you can use this series as a home inspector device.as stated on page 6. and per the maunfacturer. but you must take care of the device. it must be calibrated every year for accuracy. i have ten of these and will calbrate them once and then after two years. replace it with new.
i use two detectors per test and take the average,just as you would with e-perm devices and sometimes i will put a e-perm with the pro series and i get like reading or within 1 pico+/-

cvf

Fly Guy,

Just performed a radon test using the Sun Nuclear 1027 on a split level (two foundation types, two monitors). The home owner had his own Pro series 3. We ran concurrent tests. His results were .5 pCi/L and .6 pCi/L off of my results. Not sure how accurate the Pro Series is. By the way, I didn't see where this unit could provide a print out. How do you document the results?

Originally Posted by flyguy26

Well then, I guess I wasn't clear enough in my initial post. I know that 4 pCi/L is the threshold at which the EPA says radon should be mitigated - it's mentioned in just about every shred of literature having to do with radon, including the manual included with the device I was concerned with.

My question was geared more to the notion that there might be something wrong with the unit, since it was registering 18.4 and there was no alarm going off. Or, I thought maybe there could be a decimal point issue instead.
It seemed odd to me that, if 4.0 is the safe maximum espoused by the EPA that the device would go all the way to 999.9!

Where would you have to be for the unit to indicate 950 pCi/L?

I hope that makes my question clearer.

I can only reinforce what others have said and that is you need to take training. This posts further shows there is a lack of understanding. You owe the people you are taking money from to be better than this.

I am certified through neha.org. Hop online today and sign up.

eric

i use the pro series as stated above. what i do is snap a digital photo right there at site and then incorporate photo into report. i also have a word doc form that lists the results and all the epa data someone can get.it is all done very professional looking, because i guess it is .5 and .6 is not bad.

cvf

It doesn't look like this device is approved. National Radon Proficiency Program - Radon Testing Devices

Maybe I'm missing it though.

Thanks everyone for the great (mostly ) comments.

To everyone's great relief, I have contacted the Center for Basic and Applied Science in VA about getting proper training in radon detection.

I would like to keep the discussion going about using the Pro Series3 despite the fact that it is not on the list of NRSB approved devices:

http://www.nrsb.org/images/file/NRSB...s%20Ltg(1).pdf

The detector gets high marks for accuracy and, if used in pairs as Charlie apparently does (and calibrated annually), I would think that a viable option.

If not, can someone recommend a reasonably-priced entry-level monitoring device?

Thanks everyone for their contribution!

- Mitch

flyguy

good news for you.that is the way to go--before the lawyers start calling.
sorry to be so rough but as you see the question made many of us wonder what the $@#^.
i have used the pro series now for nine years and have put in up against and with the sun system and the e-perms during tests and the results were within the 1 pico reading. thats pretty accurate as you stated. again like all devices and by law, you must calibrate your equipment yearly.

the epa approves this device and it can be used by home inspectors, but using the manufactures guide lines CALIBRATE YEARLY

good luck in the business

cvf

Any reading over 4.0 Pci/L is to high. I use charcoal canisters from Pro Labs. I leave 2 canisters in the basement for two days and send the samples to Pro Labs where I feel you would have a more reliable reading.There recomendation if the reading is over 4.0 is too retest. That retest would verify the frist reading. After that its midigation time.

HEY AL

ever get a client to pay for a retest?? not around here.and seller will always say THAT CAN'T BE TRUE. in my nine years of inspections,have done maybe three retests. and that was requested by seller. try squeezing water out of a rock. don't know why,but it is true

cvf

Fly Guy,

You might want to consider the Sun Nuclear 1027. I have ten of these. Very accurate and approved by the IEMA-DNS (Radon testing governing body in Illinois). They are around $650.00. Be prepared to buy several as one house could take as many as four units (i.e. home with a slab, basement and a crawl plus a duplicate, if needed) Good Luck

eric

explain why you would use four units in one house? don't understand that,two readings in the lowest living area should give you all you need, crawl spaces are not liveble areas

why not take two measurements and then evaluate readings ??

cvf

If you're using a CRM like the Sun #1027 you only need one reading, and if you get a reading greater than 4.0 pCi/l you don't retest - you mitigate.

Charlie,

Each foundation type requires a separate monitor. For example.. A house with a basement, slab and a crawl would require a monitor in the basement, a monitor in the room on the slab and a monitor in the room over the crawl. My quality assurance plan required by the state of Illinois requires that I provide duplicate readings for every tenth test that I perform. So if this is the tenth test that is where the four monitors come into play. Illinois doesn't mess around. You have to be licensed here.

Charlie,

Forgot to mention that Illinois doesn't accept the Pro Series 3 for radon testing of residential properties. In fact, they (Illinois) recently sent out a letter requesting that Home inspectors do not sell these monitors to home owners as they question the accuracy of theses devices.

Eric is correct.

The EPA does not regulate radon since it's a natural occurring substance. However, some states have enacted regulations regarding testing. Some include multiple monitors, separate monitors for each foundation type and level of the home, inspector certification etc.

In unregulated states you'll probably only run into problems when you're sued or if you're dealing with a relocation company. But as professional home inspectors you shouldn't be doing testing if you haven't been through a basic measurement course and you shouldn't be doing testing with unapproved equipment, even in unregulated states.

Very intresting posts. I use the Sun Nuclear divice and do one test per house. I print out the readings at the site and the realtors love that. I have my monitors calibrated once a year at a cost of $115.00 each. The calibration chamber introduces radon at a rate of 325 pi for the duration of the test. I bought the training course from CERTI in Colorado studied it through cds in my truck day in and day out. Still listen to them on occasion. I passed the test online and got a certificate from them. In NC there are no regulations or certifications required so anyone can hold themselves out as a radon expert. 4 pi is the action level that the EPA suggests. The WHO says 2.7 should be the action level. I have 596 realtors who have me on their preferred provider lists and do around 1200 WDIIRs per year. I started doing radon measurements about 5 years ago and it has picked up this year beyound belief partly because the Real Estate Commision has added it to the contracts. Training is essential in any endevor so I would encourage anyone who does work for the public to train train train. Good luck........

jerry

first off what are you doing up at 3 am in the morning--get some sleep.

i congradulate you on passing that test from a book and on line. the radon class i took was the hardest class and test i have ever taken..had to get a 72 on test. i got a 80. and shake when i think i have to re take it this year. for recertification

go to bed

cvf

[quote=flyguy26;130158]Thanks to those of you who provided helpful information. I know that anything over 4 pCi/L is cause for concern. I was mainly asking if anyone had any experience with these particular detectors and whether they have experienced any anomalies with them since the alarm didn't go off.

I believe that what this forum is for an exchange of information and to ask questions to share information. I agree that opinions about certification is not what you were asking for.

harvey kelly

Has anybody seen the news from the WHO about them lowering their standards to 2.7 picos. As I understand the EPA will follow suit and lower their standards as well.

New Radon Limit of 2.7 Established By World Health Organization to Prevent More Lung Cancer Than EPA's 4.0 Level - Free-Press-Release.com

Originally Posted by Jerry Martin

Very intresting posts. I use the Sun Nuclear divice and do one test per house. I print out the readings at the site and the realtors love that. I have my monitors calibrated once a year at a cost of $115.00 each. The calibration chamber introduces radon at a rate of 325 pi for the duration of the test. I bought the training course from CERTI in Colorado studied it through cds in my truck day in and day out. Still listen to them on occasion. I passed the test online and got a certificate from them. In NC there are no regulations or certifications required so anyone can hold themselves out as a radon expert. 4 pi is the action level that the EPA suggests. The WHO says 2.7 should be the action level. I have 596 realtors who have me on their preferred provider lists and do around 1200 WDIIRs per year. I started doing radon measurements about 5 years ago and it has picked up this year beyound belief partly because the Real Estate Commision has added it to the contracts. Training is essential in any endevor so I would encourage anyone who does work for the public to train train train. Good luck........

I was just wondering - The EPA only authorizes only NEHA and NRSB to issue Radon testing and mitigation certifications. Each of these organizations require a proctored test. So how does an online course and test earn a valid certification? Or is it just an course on radon testing without NEHA or NRSB certification?

Originally Posted by flyguy26

Thanks to those of you who provided helpful information. I know that anything over 4 pCi/L is cause for concern. I was mainly asking if anyone had any experience with these particular detectors and whether they have experienced any anomalies with them since the alarm didn't go off.

Having said that, I don't appreciate the snotty comment from Charlie. While everyone may not be blessed with the scope and depth of Charlie's obvious intellect, there are those who are equally worthy in the trade and do a respectable job for their customers. His condescension is both unwarranted and unwanted.

flyguy26 - Virginia requires, by statute, certification and registration with the State Department of Health to provide Radon testing as a service for others. The certification must come from an EPA authorized organization, which as far I as I know is still NEHA and NRSB. You have to take an in-classroom course and pass a proctored exam. There are jerks like me who will report you if you are testing or mitigating without the proper certification. Radon testing is not like the "Mold Is Gold" money machine. With Radon, you are messing with people's lives. Get certified and do it right or don't do it at all.

Originally Posted by Stuart Brooks

flyguy26 - Virginia requires, by statute, certification and registration with the State Department of Health to provide Radon testing as a service for others. The certification must come from an EPA authorized organization, which as far I as I know is still NEHA and NRSB. You have to take an in-classroom course and pass a proctored exam. There are jerks like me who will report you if you are testing or mitigating without the proper certification. Radon testing is not like the "Mold Is Gold" money machine. With Radon, you are messing with people's lives. Get certified and do it right or don't do it at all.

Stuart,

I'm not disagreeing with you but, as I previously stated, some states do not have certification requirements for radon techs. Sure they can still obtain certification which is wise to do, but not required. In fact, I just had one of our radon techs take the course locally. They're still teaching and testing on EPA protocol from 1994.

Oops, didn't see flyguy was from Virginia.

As I stated NC requires nothing. I did take the time to take a course and paid $395.00 for it. I believe you should know what you are doing if you are going to do something. I inform everyone I do testing for that no certification is required in NC. I don't do any radon work or anything else in VA.

Originally Posted by Jerry Martin

As I stated NC requires nothing. I did take the time to take a course and paid $395.00 for it. I believe you should know what you are doing if you are going to do something. I inform everyone I do testing for that no certification is required in NC. I don't do any radon work or anything else in VA.

Thanks Jerry. Taking a Radon class when it isn't required does indicate that one is concerned about his or her profession and doing it at well as possible.

If NC doesn't require certification now, it may in the future. Support the effort or better yet, be an active part of a movement. I do know that there is at least one chapter of AARST based in NC. I went to a CE seminar in Hendersonville last summer that was held by the Blue Ridge Chapter that I believe is based in Ashland.

Originally Posted by Stuart Brooks

I was just wondering - The EPA only authorizes only NEHA and NRSB to issue Radon testing and mitigation certifications. Each of these organizations require a proctored test. So how does an online course and test earn a valid certification? Or is it just an course on radon testing without NEHA or NRSB certification?

certi is an apporved vendoe by neha-nrpp.org as a source for getting your centinuing credits to maintain your certification with them.

My initial training was proctored so I'm not sure about the initial training. But as for maintaining certification, certi and their home study courses are approved.

National Radon Proficiency Program - Continuing Education Courses

There seems to be the impression that levels below 4.0 are "safe." I doubt that you'll ever find any authoritative documents that will say that. Homes should be tested every two years because as we know, radon levels are never consistent. If the home is remodeled (even a change to the HVAC system), retest. If there is significant construction in the area, retest.

I had the opportunity to do a radon test twice on the same house within a six week period. The first reading was 0.4 and the second was 1.1. The test was done in the same location using the same meter. I guess the indication is that the house a tendency to lower radon levels.

Originally Posted by Stuart Brooks

Thanks Jerry. Taking a Radon class when it isn't required does indicate that one is concerned about his or her profession and doing it at well as possible.

If NC doesn't require certification now, it may in the future. Support the effort or better yet, be an active part of a movement. I do know that there is at least one chapter of AARST based in NC. I went to a CE seminar in Hendersonville last summer that was held by the Blue Ridge Chapter that I believe is based in Ashland.

Thanks for the plug Stuart. Yes, the Blue Ridge Chapter of AARST was founded just over a year ago and has held CE events with future goals of getting in the ear of builders and Realtors and educate them and hopefully raise the level of professionalism in the Southeast. We're probably going to have a meeting in the latter part of June and focus on our marketing/outreach efforts for the next few months. Our meetings are usually in the Asheville/Hendersonville area since that is the center of our territory.

For everyone else, by the way, the Safety Siren is intended for homeowner use NOT professional use and to date, has never been approved for use by any of the radon licensing/certification programs. I think the States of Iowa, Illinois, and New Jersey, and possibly more, have made public announcements to that fact and you'll notice the literature provided on the manufacturer's website says nothing about professional grade testing.

It does seem to be a pretty good long-term device, but just because it displays a number after 2 days, DOESN'T mean that the number means anything. The counting sensitivity is extremely low, meaning it takes a while to get enough data to be able to produce an accurate number. I've played with a few of them and it gets better after a full week, and isn't that bad after a couple of weeks, but certainly not 2-3 days.

Take the 2-day radon course, the proctored exam, and get certified. You'll be surprised home much there is to know!

SHAWN

can you provide where it stats that the pro series is not for professional inspectors. the manuel for this device says " IF USED BY PROFESSIONAL HOME INSPECTORS DEVICE MUST BE CALIBRATED EVERY YEAR". i have used this device and tested it against the sun system--the e perm devices and it gives me the same reading +/- 1 pico, just like the e-perms do and two sun system testing simultamiously.


thanks shawn
cvf

Originally Posted by CHARLIE VAN FLEET

SHAWN

can you provide where it stats that the pro series is not for professional inspectors. the manuel for this device says " IF USED BY PROFESSIONAL HOME INSPECTORS DEVICE MUST BE CALIBRATED EVERY YEAR". i have used this device and tested it against the sun system--the e perm devices and it gives me the same reading +/- 1 pico, just like the e-perms do and two sun system testing simultaneously.


thanks shawn
cvf

I've done some testing in our radon chamber and at low radon levels in the 2-3 pCi/L range against recently calibrated femto-Tech CRM-510s and an Eberline RGM-3. After several days, (like a week or two) the numbers weren't bad, but just because the display shows a number doesn't guarantee reliability. If my memory serves me correctly, the 2-3 day numbers were always low compared to the much more sensitive monitors.

Let me ask you this, which State or National credentialing program recognizes it as a professional grade monitor? Even the FSP website doesn't make those claims. So if it isn't a professional grade monitor, what liabilities does one take upon themselves by using it as such and charging for said service? Hmmm.

shawn

all i stated is that the pro series went round to round with all the other devices i tested head to head-and different devices at the same test-- and it is approved by the EPA. during real estate transaction,we inspectors are lucky to get even 48 hours to test--so short test to long test,we don't have the luxory of true proper testing-- you stated that the pro series manufacturer said it was not for professional home inspectors, but their manual contradicts that. i asked you to show me the web site proof. paragraph 6 of their manual says different. i feel that my testing is as good as the sun--the e-perm and as for charcoal--thats a dinosaur. i will do a lot of phone calls on this tomorrow, i finally have my first day off since march 2nd. interesting thread, and who says what.

let you know further tomorrow

thanks
charlie

Originally Posted by CHARLIE VAN FLEET

shawn

all i stated is that the pro series went round to round with all the other devices i tested head to head-and different devices at the same test-- and it is approved by the EPA. during real estate transaction,we inspectors are lucky to get even 48 hours to test--so short test to long test,we don't have the luxory of true proper testing-- you stated that the pro series manufacturer said it was not for professional home inspectors, but their manual contradicts that. i asked you to show me the web site proof. paragraph 6 of their manual says different. i feel that my testing is as good as the sun--the e-perm and as for charcoal--thats a dinosaur. i will do a lot of phone calls on this tomorrow, i finally have my first day off since march 2nd. interesting thread, and who says what.

let you know further tomorrow

thanks
charlie

EPA doesn't approve devices, and hasn't since 9/30/1998, which is when they privatized their Radon Proficiency Program. I know because I coordinated the administration of the device evaluations from 1991 until they shut down their program. You have probably seen a letter from EPA from, what, 2004 or so, that has essentially been retracted or superseded by another letter, whichever you want to call it.

I'm not knocking the Safety Siren, as when used properly as an ongoing or long-term test, it does well. Unplugging it every 2-3 days, taking it to another house, clearing the memory (maybe), and using the reading on the display to tell a paying client whether or not they should have the house mitigated is simply wreckless.

As I said before, show me a credentialing program that has approved the device to be used in this way, or even in pairs. You might have a difficult time finding one, just sayin.

Some folks like to fly under the radar and do things sub-par, and some want to do everything to the best of their ability. I'm just trying to help the readers know that there is a lot more to radon testing than meets the eye and if they want to do it right, they need to start with training, exams, and certification.

Charlie and others who don't believe me are free to call me if they want. I'm here to help.

Shawn

Originally Posted by James Duffin

I had the opportunity to do a radon test twice on the same house within a six week period. The first reading was 0.4 and the second was 1.1. The test was done in the same location using the same meter. I guess the indication is that the house a tendency to lower radon levels.

Those numbers are not outside of typical fluctuations in readings. Many things cause fluctuations in radon levels. One of the biggest ones is barometric pressure. I've seen fluctuations far greater than that within the same test using 1027 CRM's.

Originally Posted by John Dirks Jr

Those numbers are not outside of typical fluctuations in readings. Many things cause fluctuations in radon levels. One of the biggest ones is barometric pressure. I've seen fluctuations far greater than that within the same test using 1027 CRM's.

Yep plus wind, rain and snow or ice. I've looked at the numbers before and could tell when a cold front came through with high winds. Another test this winter had an increase that coincided with a heavy rain period. Tested a house with a bunch of kids. I could tell when the family left to go out of town over the weekend. The readings rose some when they left and went back down a little when they came home.