The easiest and quickest answer is that NIST-traceable calibration to +/-2% at 50% RH and +/-2% at 90% RH is specifically stipulated in ASTM F2170.
Flooring adhesive manufacturers have moved away from solvent-based adhesives because of high volatile organic compounds (VOCs), and the move towards more water-based adhesives has made them more susceptible to failure from higher percentages of concrete moisture. Three to five percentage points of deviation from the manufacturer's specified RH levels can create conditions for significant failure within adhesives and some flooring material types. Don't roll the dice with in situ concrete RH sensors that claim "typical tolerance" but don't meet the ASTM calibration standard. The custom-built SHT35 sensor chips inside Rapid RH® L6 single-use sensors meet the ASTM F2170 standard with a NIST-traceable certificate of calibration good for two years from the date of calibration.
