Accurately measuring moisture levels/active mold fungus

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Accurately measuring moisture levels/active mold fungus

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Kenton Shepard

Peak to Prairie Inspection Service
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Posted: Dec 12, 2005 3:20 AM       Post Subject:
If fungi commonly found in homes require 20% or greater moisture levels to remain active, then it can sometimes be crucial to test wood with an accurate moisture meter, especially in parts of the country with high humidity where levels in home materials may routinely be near the 20% mark.

Ive been using a Protimeter Surveymaster which has a conversion chart to accurately determine moisture levels between 8% and 30%. It seems to work well. The 5" probes (available in 10") allow testing of internal levels in staw bale homes, timbers, logs and wall cavities, although I haven't had a chance to use them yet.
The "Search" feature is great for finding moisture behind vinyl and tiles.

Has anyone had experience with the probes on this instrument? What have you used them for? Has anyone tested for conditions conducive to internal wood decay?

Has anyone used both the Surveymaster and Tramex (comparison)?

Kent
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Caoimh?n P. Connell
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Posted: Dec 13, 2005 1:34 PM       Post Subject:

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Hello Kent:

As I mentioned in your other post, the 20% rule isn?t really a very safe bet; simply because fungi may proliferate even where the apparent moisture content of surrounding wood is less than 20%.

Regarding the accuracy of the meters ? the actual accuracy of the meter, in the context of fungal growth, is largely a moot point, since, oddly, the moisture measured by the meters is not the same concept of moisture that is used by the fungi. In microbiological terms, water availability (i.e., the water available to the organism growing on a particular substrate) is usually discussed as water activity, (aW). Water activity is expressed as the ratio of the vapor pressure of the water in the air in equilibrium with the substance divided by the vapor pressure at the same temperature of pure water. Thus, aW values range from 1.0 (for free standing water) to 0.95 for freshly baked bread, 0.85 for salamis and summer sausages to 0.7 for hard candy and dried cereals and dried fruits.

Water content of a substance is not the same as water availability. Two substances with the same water (moisture) content may have very different aW values. Kiln-drying wood removes water which is tightly bound to molecular sites such as hydroxyl groups of polysaccharides, amino groups of proteins, and other polar sites, thus lowering water availability. Air dried wood does not release that tightly bound water since there is an equilibrium which exists between the water vapor in the air and the movement of water molecules in the substrate called the ?water potential? (a complex phenomenon dealing with the entropy of the water molecules that is beyond what any one here wants to hear about).

In general, pin moisture meters, by contrast, don?t measure moisture at all ? rather, they measure electrical conductivity. For example, I took my Tramex and placed the pins in 100% PURE water (ultra distilled water), and the moisture meter diligently read less than 10% moisture. Then, I slowly added table salt to the water, literally a grain at a time at first. As the salt content of the water increased, the moisture readings began to increase. Eventually, the meter reached a reading of 37% and did not increase any further regardless of the amount of salt in the water.

So, as always, it?s important to use instruments only within the limits of the purpose of the instrument and not attempt to extrapolate information beyond the capabilities of any instrument.

Just my thoughts!
Cheers,
Caoimh?n P. Connell
Forensic Industrial Hygienist
www.forensic-applications.com

(The opinions expressed here are exclusively my personal opinions and do not necessarily reflect my professional opinion, opinion of my employer, agency, peers, or professional affiliates. The above post is for information only and does not reflect professional advice and is not intended to supercede the professional advice of others.)

AMDG
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Kenton Shepard

Peak to Prairie Inspection Service
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Posted: Dec 13, 2005 3:43 PM       Post Subject:
Great information Caoimh?n, thank you, you're a great resource for us.

It's obviously a bad idea to be using the 20% number and making bold statements about mold fungus activity.

As part of my business I specialize in detecting internal decay in wood structural members. I'd like to use the moisture meter as an aid in testing wood members for moisture levels that will allow decay fungus to be active.

Is it possible to establish variable perameters that would then allow moisture meters to be of help in determining the presence of conditions that would allow decay fungus activity?

What I have in mind is including language in a report that would qualify a meter reading by stating something like "Decay fungus are known to be active at moisture meter reading levels near 20%, plus or minus 4% depending on local water vapor pressure levels."

The Protimeter Surveymaster is optimized to read moisture levels between 8% and 29% and the Tramex is probably similar. The Surveymaster reads 99.9% in a glass of water from my well.

As long as water remains wet, we won't need either meter for that test.

I look forward to meeting you on the 21st. I'm guessing you'll have a pretty good crowd with a tall stack of questions.

Kent
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Caoimh?n P. Connell
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Posted: Dec 16, 2005 9:06 AM       Post Subject:

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Good morning, Kent ?

I don?t know about Boulder County, but Park County has been BLOODY cold!
kshepard wrote:
Is it possible to establish variable perameters that would then allow moisture meters to be of help in determining the presence of conditions that would allow decay fungus activity?


I think so. However, there will never be a black-box technology that can be used in the absence of sound technical interpretation and experience. Moisture meters are just another tool that will allow the professional home inspector to provide valuable microbial information to the client ? but the tool is no better than the experience and knowledge of the operator.

kshepard wrote:
What I have in mind is including language in a report that would qualify a meter reading by stating something like "Decay fungus are known to be active at moisture meter reading levels near 20%, plus or minus 4% depending on local water vapor pressure levels."


I use similar language ? I report the objective readings, and then I qualify them and put them into context.

kshepard wrote:
The Protimeter Surveymaster is optimized to read moisture levels between 8% and 29% and the Tramex is probably similar. The Surveymaster reads 99.9% in a glass of water from my well.


I?m not familiar with the Protimeter Surveymaster.

I look forward to the meeting next week.


Cheers,
Caoimh?n P. Connell
Forensic Industrial Hygienist

www.forensic-applications.com

(The opinions expressed here are exclusively my personal opinions and do not necessarily reflect my professional opinion, opinion of my employer, agency, peers, or professional affiliates. The above post is for information only and does not reflect professional advice and is not intended to supercede the professional advice of others.)

AMDG
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David Andersen

David A. Andersen & Associates
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Posted: Dec 21, 2005 10:14 AM       Post Subject:
As Caoimh?n P. Connell indicated, electronic testing devices are basically used to find differential readings to indicate, locate and isolate locations for further testing. Actual content can only be determined through intrusive measures requiring laboratory analysis. Once you locate high moisture conditions, if you want to provide a greater in depth study on the material than you will have to remove a section of this material to be tested further.
This sampling technique is similar to geological testing where we use numerous types of electronic devices to identify conditions of the soil. This can be electromagnetic, ground penetrating radar or electrical inductive testing. These devices isolate the test area. Actual physical probing/core drilling must be conducted to actually remove a sample from the isolated test area for further analysis.
In many cases, unless the client wants a full qualitative analysis, electronic testing devices often are sufficient to base their decision in respect to their plan of action. If you find excessive moisture (greater than the ambient conditions and adjacent areas) this is an indication of moisture intrusion. The source of this intrusion should be identified and corrected regardless of the actual moisture content. Remediation of the excessive moisture should be conducted to lower the electronic readings to that of the surrounding area.
If you're intent is to identify conditions which are conducive to mold growth or substrate deterioration conditions, a particular measurement "action level" cannot really be set as mold can grow even in frozen conditions and deterioration will occur (but at a different rate) under any condition.

Radon testing is conducted with an electronic device. An action level of 4pCi/l is was set by the EPA in United States. This action level is not a "safe level", it is a level which is obtainable under normal mitigation procedures which are not cost prohibitive. In accordance with the EPA, no level of radiation is safe.

When testing for moisture, is there any safe level of moisture? To what extent should we strive to control this moisture? Is this information really necessary to take corrective action? Is locating a high differential of moisture readings sufficient information to base a remediation repair?

Quote:
What I have in mind is including language in a report that would qualify a meter reading by stating something like "Decay fungus are known to be active at moisture meter reading levels near 20%, plus or minus 4% depending on local water vapor pressure levels."


Is it really that important to assign numerical figures in reporting this condition? You may be opening yourself up for litigation if someone were to come back and say that they obtained a moisture level of 16% and thought they were safe, based on your report. However, a strain of mold produced adverse effects on the structure or their health. What will happen if laboratory testing was conducted and found to be substantially different than your on-site electronic tests? The radon testing devices require calibration and testing on blind Spike tests, do you have your electronic moisture meters tested and calibrated?

This maybe a little over-the-top, however when we add things into our inspection reports that are beyond the scope of excepted standards, we are risking liability and for what?

I'm even a little bit uneasy about using moisture test equipment as an indicator. There are conditions that will throw off the test results, such as increased density of the wall/floor being tested etc.. In my report I indicate "electronic testing was conducted which indicated moderate to high differential readings from the surrounding area. This may indicate excessive moisture intrusion and should be investigated further. Elevated moisture conditions are susceptible to accelerated deterioration and may promote the growth of decay fungus".
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Gary Porter

GLPs Home and Mold Inspections LLC
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Posted: Dec 22, 2005 5:18 PM       Post Subject:
Happy Holidays Caoimh?n P. Connell
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Caoimh?n P. Connell
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Posted: Dec 23, 2005 9:31 AM       Post Subject:

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Merry Christmas back to you, Brother.

And peace and blessings to all who may read this. I wish all of you a blessed and joyous Christmas.

Pax,
Caoimh?n

AMDG
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Jay Moge
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Posted: Dec 23, 2005 4:07 PM       Post Subject:

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