Gastec 91D Passive Dosl Tubes Formaldehyde HCHO (0.1 ~ 20 ppm)
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Indicator: 1 ~ 20 ppm
Measuring Range: 0.1 ~ 20 ppm
Sampling Hours: 1 to 10 hours
Colour Change: Yellow → Reddish Brown
Reaction Principle: 3HCHO + (NH2OH)3 H3PO4 → H3PO4, H3PO4 + Base+Phosphate
Coefficient of Variation: 10% (1 ~ 20 ppm-hr)
Nr. of tests: 10
Performance
| Measuring Range | 0.1 to 20 ppm |
| Sampling Hours | 1 to 10 hours |
| Detecting Limit | 0.05 ppm (10 hours) |
| Colour Change | Yellow → Reddish Brown |
| Reaction Principle |
3HCHO + (NH2OH)3 H3PO4 → H3PO4 |
| Coefficient of Variation | 10% (for 1 to 20 ppm-hr) |
| Shelf Life | 1 Year |
| Corrections for temperature & humidity | Unnecessary |
| Store the tubes in the refrigerator to keep at 10ºC (50ºF) or below. | |
Possible coexisting substances and their interferences (NOTE)
| Substance | Interference | Change colour by itself to |
| Aldehydes, Ketones, Acid gases | + | Reddish brown |
Other substance measurable with this detector tube
| Substance | Correction Factor | Sampling Time | Measuring Range |
| Acetaldehyde | 1.0 | 1 to 10 hours | 0.1 to 20 ppm |
| Furfural | 3.0 | 1 to 10 hours | 0.3 to 60 ppm |
| Methyl ethyl ketone | 1.25 | 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% |
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