Formaldehyde |
NO.91 |
| HCHO |  |
 |
Performance
| Measuring Range |
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| Number of Pump Strokes |
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| Correction Factor |
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| 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% |
