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Formaldehyde (HCHO)
Item Item Details
(Price is for domestic US market only)
Formaldehyde (HCHO)
Item Name:
Formaldehyde (HCHO)
Item #:

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Formaldehyde HCHO NO.91D



Measuring Range

0.1 to 20 ppm

Sampling Hours

1 to 10 hours

Detecting Limit

0.05 ppm (10 hours)

Color Change

Yellow Reddish Brown

Reaction Principle

Formaldehyde reacts with hydroxylamine phosphate to librate
phosphrous acid, which discolors pH indicator to reddish brown.

Coefficient of Variation

10% (for 1 to 20 ppm-hr)

Shelf Life 1 Year
Corrections for
temperature & humidity
Store the tubes in the refrigerator to keep at 10oC (50oF) or below.

Possible coexisting substances and their interferences (NOTE)



Change color by itself

Aldehydes, Ketones, Acid gases

Plus error

Discolors reddish brown

Other substance measurable with this detector tube


Correction Factor

Sampling Time

Measuring Range



1 to 10 hours

0.1 to 20 ppm



1 to 10 hours

0.3 to 60 ppm

Methyl ethyl ketone


1 to 10 hours

0.125 to 25 ppm

Calibration gas generation Diffusion tube method

TLV-TWA TLV-STEL Explosive range
- C 0.3 ppm 7.0 to 73%

Range 0.1-20

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