FP-31 Formaldehyde Portable Gas Detector by RKI Instruments

Formaldehyde Gas Detector



  • Built-in sample draw pump
  • Photoelectric photometry technology
  • Direct digital readout
  • Colorimetric detection tablet method
  • No false readings from interfering gases
  • Operates on 4 AA
  • Stores 99 readings
  • No warm up time
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The FP-31 is a highly sensitive portable gas detector specific for formaldehyde detection. It uses a photoelectric photometry method which utilizes colorimetric tablets for detection. A tablet in placed into the instrument, and then a room air sample is pumped onto the tablet for either a 15 minute or a 30 minute period. If formaldehyde is present, it will cause the chemically impregnated tablet surface to darken or stain. The magnitude of the stain directly correlates to the level of formaldehyde in the air. The stain darkness is read by an optical sensor in the FP-31, and then the instrument calculates the formaldehyde concentration. The FP-31 then has a direct readout of the formaldehyde measurement on an easy to read LCD display. The unit is capable of detecting very low levels of formaldehyde, in order to confirm if an area contains safe breathing levels. There are no known interfering gases, as shown on the chart on the reverse side of this sheet.


  • Furniture and woodworking
  • Coating and varnishing
  • Engineered wood products
  • Medical / veterinary
  • Painting & corrosion resistant finishes
  • Carpet manufacture & storage
  • Adhesives
  • Heat treatment operations
  • RV / trailer / mobil home inspecting

Detection Ranges

30 minute sample 0 – 0.4 ppm (0.005 ppm/digit)
15 minute sample 0 – 1.0 ppm (0.01 ppm/digit)


Detection gas Formaldeyde (HCHO) in air
Detection range 0-0.4 ppm (0.005ppm/digit) 0-1.0 ppm
(0.01 ppm/digit)
Detection time 30 minutes (1,800 sec.) 15 minutes (900 sec.)
Detection principle Photoelectric photometry method
Detection method Colorimetric tablet method (accumulating measurement)
Accuracy ± 20% of reading or ± 5% of full scale (which ever is greater)
Display Digital LCD
Sampling method Sample drawing with built-in pump
Operating conditions -10 ~ 40ºC (14 ~ 104ºF), below 90%RH
Memory Up to 99 readings (automatic recording at the completion of measurement)
Self-diagnosis Failure of light source and light receiver, low battery voltage, pump failure, system trouble
Power Source AA size Alkaline batteries (quantity 4)
Continuous Operation Approximately 12 hours (with no alarm or backlight, with alkaline batteries at 20°C)
Dimension Approx 85(W) x 190(H) x 40(D)mm, 3.35(W) x 7.48(H) x 1.57(W),
Weight 500g, 17.6 oz
Standard Accessories • Detection TAB (20 pcs/pack) ** • AA size alkaline batteries • Operating manual
Optional Accessories Zero and span tab, datalogging software, USB-IRdA cable (for downloading stored data)
Warranty One year material and workmanship


Interference against other gases (typical)
Test Gas Concentration Reading
Toluene 1.0 vol.% 0 ppm
Benzene 1.0 vol.% 0 ppm
Acetoaldehyde 100 ppm 0 ppm
Carbon monoxide 50 ppm 0 ppm
Carbon dioxide 1.0 vol.% 0 ppm
Ammonia 25 ppm 0 ppm
Acetone 1.0 vol.% 0 ppm


Field Test Verification Data
Measurement Place FP-31 DNPH method*
Interior 0.020 ppm 0.025 ppm
Locker 0.030 ppm 0.03 ppm
Furniture 0.040 ppm 0.05 ppm


* Dinitrophenylhydrazine detection method

** Please note: Detection tabs have a six month shelf life. They must be stored in a refrigerator (37°F – 50°F, 3-10°C)

Specifications subject to change without notice.

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