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ClearStak is the first EPA approved testing facility for partial thermal storage. Under  ISO-IEC 17025, the testing services offered are: 


  • Method 28 (Certification & Auditing of Wood Heaters)  

  • Method 28 WHH

  • Method 28 WHH Partial Thermal Storage

  • Portable Particulate Testing 

 Testing can be performed on the following appliances: 


  • Indoor and Outdoor Hydronic Heaters

  • Pellet Stoves 

  • Woodstoves 


Need to get tested? 
Start by completing this worksheet. 
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