Rapid RH Moisture Test Frequently Asked Questions (FAQ)
- What is relative humidity in concrete?
- What are acceptable levels of relative humidity?
- When talking about moisture testing, what does equilibration mean?
- Is there a correlation between relative humidity percentage and Moisture Vapor Emission Rate (Lb/1000 Sq Ft/24 Hr) measured with calcium chloride testing?
- How many relative humidity tests should I use on each job?
- How important is sensor calibration?
- What’s the difference between the Rapid RH® System and a concrete moisture meter?
- What are the advantages of Wagner Rapid RH® 4.0 EX Smart Sensor Technology over other relative humidity instruments?
- Who is qualified to measure relative humidity using Rapid RH® system?
- Has there been a change to the Rapid RH® Easy Reader?
- What is Touch-n-Sense Technology™?
- Can I use my old Rapid RH® Easy Reader with the new Rapid RH® 4.0 EX Smart Sensors?
- Does Wagner sell a Rapid RH® Easy Reader that displays degrees Celsius?
- Once activated, how long will the display on the Rapid RH® Easy Reader stay on?
- Can I use the Rapid RH® System even if the HVAC isn’t on?
- Can I replace the Rapid RH® Easy Reader’s battery?
- Why do some Rapid RH® 4.0 EX Smart Sensors fit very tightly in the drilled holes?
- How do I properly install the new Rapid RH® 4.0 EX Smart Sensors, including extension sleeves?
- My Rapid RH® Easy Reader is not fitting into the Rapid RH® 4.0 EX Smart Sensor, What can I do?
- Does my Rapid RH® Easy Reader need to be calibrated periodically?
- Some water spilled into one of our Rapid RH® 4.0 EX Smart Sensors – Is it ruined?
- Why do I see “ER” (Error) on the Rapid RH® Easy Reader display?
- My Rapid RH® Easy Reader screen is frozen or doesn’t come on. What do I do?
- My Rapid RH® Easy Reader came with plastic protective end caps – Do I need to keep them?
- My orange cap was missing when I went to take a reading. Do I need to have the cap on to ensure equilibration?
- How can I learn more about concrete drying and measuring moisture in concrete?
Q: What is relative humidity in concrete?
A. Relative Humidity is the actual amount of moisture in the air compared to the amount of moisture that the air could hold if saturated, expressed as percent. In concrete, you measure the relative humidity of a small volume of air at the bottom of a hole drilled into the concrete.
Q: What are acceptable levels of relative humidity?
A: The type of flooring product to be installed determines the acceptable level of relative humidity. Different RH specifications apply to different materials such as resilient flooring, wood, or epoxy coatings. Check with the floor-covering manufacturer for a relative humidity specification. Many flooring manufacturers and industry associations recognize and specify relative humidity testing. ASTM F710 gives general industry guidelines. Typical relative humidity requirements range from 75% to 90% RH, depending on the flooring product. For a list of manufacturers’ RH specifications, please visit www.rhspec.com.
Q: When talking about moisture testing, what does equilibration mean?
A: Equilibration or stability occurs when a drilled hole achieves thermal and moisture equilibrium. For the accuracy of the readings it is necessary to wait until equilibrium is restored after drilling. In most cases the Rapid RH® 4.0 EX Smart Sensor will be within 3% of the final reading one hour after installation. Follow ASTM F2170 procedures pertaining to equilibration time. Once equilibration is achieved, future readings can be taken instantly with the Rapid RH® Easy Reader.
Q: Is there a correlation between relative humidity percentage and Moisture Vapor Emission Rate (Lb/1000 Sq Ft/24 Hr) measured with calcium chloride testing?
A: There is no correlation between the tests. Relative humidity testing is a measure of moisture condition in the concrete. When a floor covering is placed on top of a slab, it restricts evaporation from the top surface of the slab; moisture within the slab then distributes itself to achieve equilibrium due to temperature and chemical interactions from the top to the bottom of the slab. In the long run, adhesive and flooring are then exposed to the equilibrium moisture condition at the top of the slab. The calcium chloride test does not reflect the long-term moisture situation that will be established by equilibration and can even artificially pull moisture out of the top few centimeters of the slab. Rapid RH® 4.0 EX Smart Sensors measure the relative humidity that will exist after the floor is covered. See the Measuring Relative Humidity at the Correct Depth chart.
Q: How many relative humidity tests should I use on each job?
A: For the Flooring Contractor and as part of the project documentation process, ASTM F2170 requires that 3 tests be placed in the first 1,000 sq. ft. and one test be placed every 1,000 sq. ft. thereafter. If you are using the Rapid RH® system as a monitoring tool early in a project to determine when final acceptance testing should be performed, several Rapid RH® 4.0 EX Smart Sensors can be placed throughout the floor 28 days after the pour and readings taken as often as desired.
Q: How important is sensor calibration?
A: Sensors must have a current, accurate calibration at the time of use to provide trustworthy results. Rapid RH® 4.0 EX Smart Sensors are supplied with a calibration certificate to prove traceability to the U.S. National Institute of Standards and Technology (NIST) as specified by ASTM F2170 section 6. Reusable moisture probes must be periodically checked or returned to the manufacturer for re-calibration.
Q: What’s the difference between the Rapid RH® System and a concrete moisture meter?
A: Moisture meters should never be used to make the final determination as to whether or not a concrete slab is dry enough for a flooring installation. Here’s why:
No ‘moisture meter’ of any type can give consistently accurate ‘moisture’ readings across the different mixes and densities of concrete. Other components (metal reinforcing bar, aggregate size and amount, etc.) can also cause false indications of ‘moisture’, especially with non-pin meters. Pin-type ‘moisture’ meters are also not practical for moisture measurement because variable chemical and physical characteristics in concrete can cause false readings due to changes in electrical resistance that have nothing to do with moisture.
Even if the so-called ‘concrete moisture meters’ were sufficiently accurate, they only measure ‘moisture’ (not relative humidity) in a very small area near the surface of the concrete slab. This type of surface ‘moisture’ testing says nothing about the conditions inside the slab. Once a floor covering is placed on a concrete slab, the relative humidity (RH) within the slab will equilibrate throughout the thickness of the slab. A slab that may have been “dry” (low RH) at the surface (without a floor covering) will see a higher RH (migrated from within the concrete) at the surface when the floor covering has been installed.
Rapid RH® system gives a relative humidity reading from within the slab for a much more accurate picture of what the final relative humidity reading will be under an installed floor covering or coating.
Q: What are the advantages of Wagner Rapid RH® 4.0 EX Smart Sensor Technology over other relative humidity instruments?
A: Rapid RH® 4.0 EX Smart Sensors fully comply with ASTM F2170. They are installed below the surface of the concrete slab, so there is far less risk of damage to the sensors or interference to normal activity on the floor. Once the Smart Sensors have been placed and equilibrated, future readings can be taken immediately without any further equilibration time. The Rapid RH® relative humidity testing system significantly improves the ability to monitor the drying progress of new and existing concrete slabs without adding substantial cost to the project. With the Rapid RH® Easy Reader, jobsite personnel can easily monitor the drying progress of a slab for any period of time with minimal training. There is no need for a testing agency return to the jobsite with their instruments to obtain more results.
Q: Who is qualified to measure relative humidity using Rapid RH® system?
A: Anyone who follows ASTM F2170 “Standard Test Method for Determining Relative Humidity in Concrete Floor Slabs Using in situ Probes.” Once the Rapid RH® 4.0 EX Smart Sensors are installed, jobsite personnel can easily monitor the drying progress of a slab with minimal training. Checklist of steps to follow when taking RH readings.
Q: Has there been a change to the Rapid RH® Easy Reader?
Q: What is Touch-n-Sense Technology™?
A: Touch-n-Sense™ is our patent pending technology, integrated into the Rapid RH® Easy Reader to enable it to automatically take a reading when placed in contact with the Rapid RH® 4.0 EX Smart Sensors. Once the bottom of the Easy Reader makes contact with the Smart Sensor, the Easy Reader comes to life, takes a reading and holds it for 5 minutes, even when removed from the test hole, before turning itself off. It’s just that easy.
Q: Can I use my old Rapid RH® Easy Reader with the new Rapid RH® 4.0 EX Smart Sensors?
Q: Does Wagner sell a Rapid RH® Easy Reader that displays degrees Celsius?
A: Yes. Rapid RH® Easy Reader that display temperature in Celsius can be distinguished by blue labels and blue plastic protective end caps. Please visit our Online Store or call 1-800-634-9961 to learn more.
Q: Once activated, how long will the display on the Rapid RH® Easy Reader stay on?
Q: Can I use the Rapid RH® System even if the HVAC isn’t on?
A: ASTM F2170 specifies that the floor must be at service conditions (building and room enclosed and the HVAC running). Relative humidity is calculated with temperature, so a significant difference between the temperature of the slab when testing, and what it will be “in service” is an important consideration. However, relative humidity testing performed 40% below the surface of the concrete is less likely to be affected by the ambient conditions than calcium chloride testing or other surface testing methods, which are affected greatly by ambient conditions.
Q: Can I replace the Rapid RH® Easy Reader’s battery?
A: Yes. The Rapid RH® Easy Reader comes with two AAAA alkaline batteries. If battery is low, the display will read “LO.” Replace batteries immediately. To replace the batteries, open up the battery cover by removing the one battery cover screw with a jeweler’s Philips screwdriver. DO NOT OPEN UP THE FULL BODY OF THE Easy Reader AT ANY TIME.
Q: Why do some Rapid RH® 4.0 EX Smart Sensors fit very tightly in the drilled holes?
A:Rapid RH® 4.0 EX Smart Sensors should be placed in holes drilled with a 4 fluted, carbide-tipped drill bit that falls within the specifications for an ANSI standard ¾” bit. This range is from 0.775” to 0.787”. A tight-fitting Rapid RH® 4.0 EX Smart Sensor is most likely caused by one of two reasons: The first reason could be that your drill bit has “worn” down with use and has lost some of its “diameter”. This will most likely become noticeable after about 60-70 holes drilled. The other reason could be that you have purchased a new drill bit that is on the lower end of the tolerance spectrum for diameter.
Q: How do I properly install the new Rapid RH® 4.0 EX Smart Sensors, including extension sleeves?
A: Please view our detailed installation manual.
Q: My Rapid RH® Easy Reader is not fitting into the Rapid RH® 4.0 EX Smart Sensor, What can I do?
A: In a few instances, even if you have a properly dimensioned drill bit, the Rapid RH® 4.0 EX Smart Sensor housing may have been deformed when inserted into the concrete. Deformation is most likely to occur if one does not use the proper insertion tool. Use the Insertion Tool that came with the Rapid RH® Complete Starter Kit (also available at the Rapid RH® online store) to re-form the Smart Sensor housing by inserting the tool and pressing down to re-shape the Smart Sensor housing. This method works quite well to re-form the Smart Sensor housing to the appropriate dimensions.
Q: Does my Rapid RH® Easy Reader need to be calibrated periodically?
A: No. Each Rapid RH® 4.0 EX Smart Sensor has an embedded calibration from the factory. The Easy Reader simply displays what the Smart Sensor tells it. That is what makes the Smart Sensor and Easy Reader an intelligent system.
Q: Some water spilled into one of our Rapid RH® 4.0 EX Smart Sensors – Is it ruined?
A: It is very likely that the Rapid RH® 4.0 EX Smart Sensor will continue to function properly after water is removed from inside the Smart Sensor housing, for example, by vacuuming. However, if water ran down into the drilled hole around the Smart Sensor housing, then the concrete in that area may be damp; drill a new hole and install a new Smart Sensor to assure accurate and useful results.
Q: Why do I see “ER” (Error) on the Rapid RH® Easy Reader display?
A: The Rapid RH® Easy Reader may not be properly communicating with the Rapid RH®4.0 EX Smart Sensor for the following reasons: (1) The Easy Reader was not in contact with the Smart Sensor long enough. Hold the Easy Reader in the Smart Sensor until the first relative humidity reading appears on the screen, then remove. (2) Debris is blocking proper contact. Check the Smart Sensor housing for any debris. Vacuum out the Smart Sensor.
Q: My Rapid RH® Easy Reader screen is frozen or doesn’t come on. What do I do?
Q: My Rapid RH® Easy Reader came with plastic protective end caps – Do I need to keep them?
Q: My orange cap was missing when I went to take a reading. Do I need to have the cap on to ensure equilibration?
A: No. Each Rapid RH® 4.0 EX Smart Sensor isolates the measuring environment from the outside air using a 2-stage redundancy isolation ring system. As the Smart Sensor is “seated” within the hole, the first stage is a vertical ring on the lowest portion of the Smart Sensor that seals the bottom angle of the drilled hole. At right angles to that, the second stage ring seals off the sidewall of the concrete hole just above the first stage. Equilibration is assured. However, always replace a missing cap to protect the Smart Sensor and minimize debris from getting into the housing when installed on a jobsite.
Q: How can I learn more about concrete drying and measuring moisture in concrete?
A: The following are excellent resources:
Books, articles and seminars by Howard Kanare, Senior Principal Scientist, CTLGroup:
Concrete Floors and Moisture 2nd edition, Portland Cement Association, 164 pp, 2008.
“Why Are We Still Having Problems with Concrete Floors and Moisture?”
Concrete Construction Magazine, 2007 Special Floors Issue, December 2007.
“302.2R-06: Guide for Concrete Slabs that Receive Moisture-Sensitive Flooring Materials”, Reported by ACI Committee 302, American Concrete Institute
“Standard Test Method for Determining Relative Humidity in Concrete Floor Slabs Using in situ Probes”, Designation: F2170, ASTM International.