| |
|
|
|
Formaldehyde |
|
NO.91 |
|
HCHO |
 |
|
Performance |
|
|
Measuring Range |
|
2 to 20 ppm |
20 to 50 ppm |
50 to 100
ppm |
|
|
Number of Pump
Strokes |
|
|
Correction Factor |
|
|
Sampling Time |
1
minute per pump
stroke |
|
Detecting Limit |
0.5 ppm (n=2) |
|
Colour Change |
White → Brown |
|
Reaction Principle |
HCHO + C6H4(CH3)2
+ H2S2O7
→ Condensation
Polymer |
|
Coefficient of
Variation |
15% (for 2 to 6 ppm),
10% (for 6 to 20 ppm) |
|
Shelf Life |
3
Years |
|
Corrections for
temperature &
humidity |
Unnecessary |
|
Store the tubes at
cool and dark place. |
|
|
Possible coexisting substances and
their interferences
(NOTE) |
|
Substance |
Concentration |
Interference |
Change colour by itself to |
|
Aldehydes |
1/2 time |
+ |
Brown |
|
Esters, Ethers |
1000 ppm |
+ |
No |
|
Ketones |
1000 ppm |
+ |
No |
|
Styrene |
500 ppm |
+ |
Yellow |
|
|
Calibration gas generation |
Diffusion tube method |
|
TLV-TWA |
TLV-STEL |
Explosive range |
|
- |
C 0.3 ppm |
7.0 to 73% |
|
|
|
|
|
|
Gastec Tubes and
Sampling Pump
