Leader in Measurement Technology

FP-31 Formaldehyde Gas Detector


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 gasFormaldeyde (HCHO) in air
Detection range0-0.4 ppm (0.005ppm/digit)
Detection time30 minutes (1,800 sec.)
Detection principlePhotoelectric photometry method
Detection methodColorimetric tablet method (accumulating measurement)
Accuracy± 10% of reading or ± 5% of full scale (which ever is greater)
DisplayDigital LCD
Sampling methodSample drawing with built-in pump
Operating conditions-10 ~ 40ºC (14 ~ 104ºF), below 90%RH
MemoryUp to 99 readings (automatic recording at the completion
of measurement)
Self-diagnosisFailure of light source and light receiver, low battery voltage,
pump failure, system trouble
Power SourceAA size Alkaline batteries (quantity 4)
Continuous OperationApproximately 12 hours (with no alarm or backlight,
with alkaline batteries at 20°C)
DimensionApprox 85(W) x 190(H) x 40(D)mm, 3.35(W) x 7.48(H)
x 1.57(W),
Weight500g, 17.6 oz
Standard Accessories• Detection TAB (20 pcs/pack) ** • AA size alkaline batteries • Operating manual
Optional AccessoriesZero and span tab, datalogging software, USB-IRdA cable
(for downloading stored data)
WarrantyOne year material and workmanship

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Interference against other gases (typical)
Test GasConcentrationReading
Toluene1.0 vol.%0 ppm
Benzene1.0 vol.%0 ppm
Acetoaldehyde100 ppm0 ppm
Carbon monoxide50 ppm0 ppm
Carbon dioxide1.0 vol.%0 ppm
Ammonia25 ppm0 ppm
Acetone1.0 vol.%0 ppm
Field Test Verification Data
Measurement PlaceFP-31DNPH method*
Interior0.020 ppm0.025 ppm
Locker0.030 ppm0.03 ppm
Furniture0.040 ppm0.05 ppm


  • 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