| 被動擴(kuò)散式檢測管是用來測定較長時間下氣體濃度的時量平均值（TWA），采用自然擴(kuò)散的方式。 這種檢測管里面填充有吸附劑及反應(yīng)劑，氣體以一定的速率被均勻吸附，從而出現(xiàn)較為明顯均勻的變色。 檢測工作場所人員的有害氣體暴露量時，用右圖的檢測管夾（710）放置在人員衣領(lǐng)處即可。 檢測有害氣體在工作場所的分布時，把該檢測管固定放置一段時間后就可檢測出來。也可用來進(jìn)行長時間的檢測。 | |
特點 簡潔，輕巧，方便多用 直接讀數(shù) 不需取樣設(shè)備 圖例 A-切斷處 B-吸附劑 C-檢測劑 | 檢測管夾 No. 710 |
Performance
| Measuring Range | 2 to 600 ppm |
| Sampling Hours | 1 to 10 hours |
| Detecting Limit | 2 ppm (10 hours) |
| Colour Change | Yellow → Reddish Brown |
| Reaction Principle | 3CH3COC2H5+ (NH2OH)3H3PO4 → H3PO4 H3PO4 + base → Phosphate |
| Coefficient of Variation | 10% (for 20 to 600 ppm-hr) |
| Shelf Life | 2 Years |
| Corrections for temperature & humidity | Temperature correction is necessary |
| Store the tubes in the refrigerator to keep at 10ºC (50ºF) or below. | |
Possible coexisting substances and their interferences (NOTE)
| Substance | Concentration | Interference | Change colour by itself to |
| Aldehydes | + | Reddish brown | |
| Ketones | + | Reddish brown | |
| Acid gases | + | Reddish brown (Unclear demarcation) |
Other substance measurable with this detector tube
| Substance | Correction Factor | Measuring Range |
| Acetone | 0.7 | 1.4 to 420 ppm |
| Methyl isobutyl ketone | 2.0 | 4 to 1200 ppm |
| Acetaldehyde | 0.6 | 1.2 to 360 ppm |
| Calibration gas generation | Diffusion tube method |
| TLV-TWA | TLV-STEL | Explosive range |
| 200 ppm(2014) | 300 ppm(2014) | 1.7 to 11.4% |
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