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Formaldemeter™ 400ST (Exclusive to Suzhou Stanford Instruments Ltd)







The latest 3-parameter instrument from PPM Technology directly measures airborne formaldehyde concentrations as well as ambient temperature and humidity levels. The PPM 400ST is exclusive to our distributor Suzhou Stanford Instruments Ltd. in the P.R.C. and has also been awarded a P.A. Certificate.

Building on the technology developed in the popular Formaldemeter 400, with the addition of unique compensation techniques, the 400ST can now accurately measure low levels of formaldehyde — even in humid conditions — while still maintaining ease of use and simple calibration.

With further importance being put on air quality in public buildings, the workplace and in homes, the 400ST is aimed toward being the most accurate monitor while still providing quick and simple operation from a hand-held device.

  • Displays formaldehyde concentration in both parts per million (ppm) and mg/m³.
  • Immune to extremes of humidity and temperature thanks to a unique sampling method.
  • Simple calibration procedure can be carried out in a few minutes after only minimal training — the full kit contains a field calibration standard (6 months shelf-life) and a comprehensive operation manual.
  • Fast sampling by pressing a single button and quick recovery from normal concentrations.
  • Full range of accessories available including rear stand or wall mount for hands-free operation and PC remote control software for data logging. See separate brochure for more details.
  • Service centres throughout the P.R.C. and full technical support provided under a comprehensive manufacturers warranty.
  • Manufactured to ISO 9001:2015 quality standards and compliant to CE regulations.



Sampling Method 10ml snatch-sample of air taken by internal pump.
Sampling Frequency 2 minutes in normal IAQ conditions.
Response Time 60 seconds in 'high accuracy' mode,
approx. 8 seconds in 'lower accuracy' mode.
Mechanical 150 x 80 x 34mm ABS plastic case.
Padded accessory-case 266 x 230 x 50mm.
Weight 270g with 9v PP3 alkaline battery
Total kit weighs 750g.


Formaldehyde Sensor


Type Electrochemical manufactured by PPM Technology..
Range 0-10ppm as standard (0- 12.3 mg/m³ at 25°C).
Extended range available on request.
Resolution 0.01 ppm
Precision 2%
Accuracy 94% of all instrument readings meet the NIOSH criteria for an acceptable method when measuring 0.3ppm of formaldehyde over a relative humidity range of 25-70%. The NIOSH criterion for acceptability is that all results fall within ±25% of the true value at the 95% confidence level.
Calibration By user with supplied calibration standard or by original manufacturer.


Temperature & Humidity Module


Type Interchangeable digital CMOSens®..
Range -40 to +128°C, 0–100% RH
Accuracy ±0.4°C, ±3% RH
Optional upgrade to ±0.3°C, ±1.8% RH
Calibration Calibrated to ISO/IEC17025 by manufacturer. Traceable by the ‘National Institute of Standards and Technology' and the ‘National Physical Laboratory'.


Kit Contents


  • Formaldemeter 400ST instrument with battery
  • Formaldehyde calibration standard tube
  • Pack of phenol filters (10)
  • Ball point pen
  • Operation manual






  • Calibration Standard: Suzhou Stanford Instruments Ltd. supplies an easy-to-use formaldehyde calibration standard tube for checking and adjusting the calibration of the PPM 400ST. The tube produces a known concentration of formaldehyde vapour that can be sampled by the instrument to check accuracy and performance. The standard has a 100-sample capacity or a useful life of six months (whichever occurs sooner).
  • PPM AMS-2 Aldehyde Monitoring Station: The PPM AMS-2 enables the PPM 400ST to be used as a data logging semi-continuous formaldehyde area monitor. The AMS-2 is a compact bench top unit that connects to the hand held instrument and essentially automates the operation of the PPM 400ST.
  • SPC-1 System: The Single Point Control System enables formaldehyde monitoring to be carried out at one or more location simultaneously. Several monitoring points can be connected to the system and monitored at a central location via one PC.
  • Desk Stands and Wall Brackets: When the hand-held is used in continuous or automated modes with the AMS-2, SPC-1 or i/fB then a range of special brackets are available so that the htV can be placed in the ideal position to achieve the best results. By mounting the 400ST on a wall then samples can be taken at head-height - the area of air that is being breathed by the occupants.


Comparison of Formaldemeter 400 & PPM 400ST Performance with various Humidity Conditions.

Instrument Readings
(mean ± StDev)
400 400ST
0.1ppm 25 0.00±0.000 0.13±0.025
50 0.12±0.016 0.10±0.018
70 0.23±0.042 0.10±0.016
0.3ppm 25 0.11±0.047 0.34±0.020
50 0.30±0.027 0.31±0.030
70 0.37±0.031 0.30±0.020

All concentrations in ppm.

Data based on the average readings of 12 instruments. Formaldehyde gas stream generated by a permeation tube device traceable to NIST.





With the use of formaldehyde in industry and the recent issues raised in public health and indoor air quality typical applications might include:

  • Medical Care & Sterilisation
  • Pharmaceuticals
  • Agriculture
  • Fumigation
  • Paint and Paper manufacture
  • Textiles & Dye manufacture
  • Particle & Laminate Boards
  • Building Management
  • Air Conditioning system management
  • Environment and Public Health Agencies


For further information…

Contact Suzhou Stanford Instruments Ltd. directly:

Suzhou Stanford Instruments Ltd.
4/F, 3 Jinshan Rd,
Suzhou New District 215011,
Jiangsu Province

Tel: 0086-(0)512-68242417,68242453
Fax: 0086-(0)512-68241092
Web: www.cn-stf.com
Email: stf@cn-stf.com

or contact PPM Technology Ltd. who will pass on your details.


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