How to Read the RH Test Strip:

How to read the RH Test Strip                   Need Help?

The Test Strip Dots will change from pink to blue (left to right) as relative humidity (RH) increases and from blue back to pink (right to left) as RH decreases.  The changes between two circles can be subtle, especially as the RH  is close to the top of one band and the bottom of the next. 



If the color is:


RH Test Strip Pink Dot    Pink - Indicates the RH is above the range of the RH value listed above the dot.

   Lavendar- Indicates the RH is around the mid-point of the range of the RH value listed above the dot.

        If the dot is more towards Pink the RH falls in the lower half.

        If the dot is more Blue the RH falls in the upper half.

   Blue - Indicates the RH isbelow the range of the RH value listed above the dot.




RH Test Strip Example:


The RH read at the time the image was captured was 57%


  1.  40% RH Dot is Pink (Above 40% RH)
  2.  60% RH Dot is Blue (Below 60% RH)
  3.  50% RH Dot is between Pink and Blue, but closer to blue so RH Falls in upper half (55%-60% RH)

Do I Have An RH Problem?:

High and Low Relative Humidity (see table below) can wreak havoc on items and people, but so can rapid swings in RH. 


Unchecked rapid changes of RH even within "Safe" ranges can cause warping, cracking, fatique, condensation and other problems.


You may have an RH problem if your log indicates:

  • RH  > 50% on regular basis
  • RH Exceeds 60%+ at any time 
  • Swings of 10%-20% or higher in a day


Contact Us for a Free No Obligation RH Consult




Optimum RH Ranges:

Item RH Range Notes
Leather 40%-60% Reduces cracking, maintains pliability, quality and appearance
Paper 40%-50% High RH allows rot and discoloration
Mold and Mildew Prevention <50% The majority of molds and Mildews go dormant below 50% RH, but will flourish again if RH exceeds 50% in the future 
Dust Mite Elimination <50% Adults die within 2 weeks, dormant larva months and may evolve if moisture returns
Eliminate or Reduces Metal Corrosion <50% Corrosion of metals depends on a number of factors, but RH > 50% shows exponential increase for damage
Electronics 40%-50% Range prevents corrosion, moisture damage and static buildup
Occupied Spaces (Offices) 30%-40% Keeps carpeting, fabrics, papers in range to prevent damages
Libraries/Museums 40%-55% Different collection types, need different RH levels, but the stated range is common recommendation
Woodwork 40%-60% Warping, softening and insect infestation may occur in the higher RH levels
Human Comfort 30%-80% RH comfort levels are also driven by temperature

Table Guideline Data Aggregated from an number of Goverment and Industry Sources sand hould not be used as a final guide for your situation.





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