Draeger MicroTubes vs short-term tubes: the ppb system and when the handbook describes each
A Draeger short-term tube is read by eye: a fixed number of pump strokes, a stain, a printed scale, a result in ppm or vol.-% within a stated standard deviation. A Draeger MicroTube is read by the X-act 7000 analyzer: each MicroTube set gives 10 measurements in succession, the substance-specific reaction layers and pre-layers in the glass capillaries filter out other substances, and the calibration data for a typical period of use of one year is stored on an RFID tag, calibrated at 20 °C and 50 % relative humidity with correction factors for temperature and humidity (p. 81). The analyzer’s camera evaluates discolorations the eye cannot see and includes the speed of the color change, which is how the system reaches the low ppb range; the handbook states the accuracy of all MicroTubes is less than or equal to ± 25 % (pp. 80–81, 90).
Draeger Benzene MicroTubes for X-act 70001 to 150 ppb, 0.15 to 10 ppm and 10 to 100 ppm versionsWhy a second system? The handbook gives the reasons in its chapter 3 summary: sensitivity (extremely low ppb concentrations), selectivity (pre-layers that largely eliminate cross-sensitivities, so fewer false positives), versatility (MicroTubes for different gases and vapors) and ease of use (insert, start, read). The benzene example on this site shows the gap: the lowest short-term benzene tube, 0.25/a, starts at 0.25 ppm; the benzene MicroTube starts at 1 ppb. For hydrogen sulfide the short-term tubes start at 0.2 ppm and the MicroTube at 0.1 ppm; for formaldehyde 0.2 ppm against 5 ppb. The short-term tube remains the instrument that needs no electronics, no battery and no analyzer, and reads at once with a hand pump.
Short-term tube and MicroTube, point by point
The MicroTubes on this site, by gas
- A, c, e, t, o, n, e, ,, , a, l, c, o, h, o, l, s, ,, , a, m, m, o, n, i, a, ,, , b, e, n, z, e, n, e, ,, , 1, ,, 3, -, b, u, t, a, d, i, e, n, e, ,, , c, a, r, b, o, n, , d, i, o, x, i, d, e, ,, , c, a, r, b, o, n, , m, o, n, o, x, i, d, e, ,, , c, h, l, o, r, i, n, e, ,, , e, t, h, y, l, e, n, e, , o, x, i, d, e, ,, , f, o, r, m, a, l, d, e, h, y, d, e, ,, , h, y, d, r, o, c, h, l, o, r, i, c, , a, c, i, d, ,, , h, y, d, r, o, g, e, n, , c, y, a, n, i, d, e, ,, , h, y, d, r, o, g, e, n, , s, u, l, f, i, d, e, ,, , m, e, r, c, u, r, y, ,, , M, T, B, E, ,, , n, i, t, r, o, g, e, n, , d, i, o, x, i, d, e, ,, , n, i, t, r, o, u, s, , f, u, m, e, s, ,, , p, e, r, c, h, l, o, r, o, e, t, h, y, l, e, n, e, ,, , p, e, t, r, o, l, e, u, m, , h, y, d, r, o, c, a, r, b, o, n, s, ,, , p, h, o, s, g, e, n, e, ,, , s, u, l, f, u, r, , d, i, o, x, i, d, e, ,, , t, o, l, u, e, n, e, ,, , x, y, l, e, n, e, .
- Each gas page lists the MicroTubes under the short-term tubes with their ranges, so the ppb and the ppm instruments for one gas are on one screen.
- MicroTubes are read only on the X-act 7000; short-term tubes only on the accuro or X-act 5000 (handbook chapter 3, section 2.3).
Questions people ask
What is a Draeger MicroTube?
A small glass capillary with substance-specific reaction layers and pre-layers, read by the X-act 7000 analyzer; each set gives 10 measurements and carries its calibration on an RFID tag (handbook pp. 80–81).
Can a MicroTube be read by eye or with a hand pump?
No; the X-act 7000 opens the capillary, draws the flow and reads the color change with a camera (p. 81).
How low can MicroTubes read?
The low ppb range; benzene MicroTubes on this site start at 1 ppb and formaldehyde at 5 ppb.
How accurate are MicroTubes?
The handbook states the accuracy of all MicroTubes is less than or equal to ± 25 % (p. 90).
Do MicroTubes have cross-sensitivities?
The pre-layers filter out other substances so the measurement largely depends on the target substance, which the handbook says largely eliminates cross-sensitivities and false positives (p. 80).
Related guides
Draeger X-act 5000 and X-act 7000: two different instruments, and what each one readsX-act 5000 and X-act 7000What is cross-sensitivity on a Draeger tube, and how is it listed?Cross-sensitivityWhich Draeger tube range covers the OSHA PEL or the IDLH? Reading the limits next to the rangesRange and exposure limitsWhat do Draeger tubes measure? The gases, the ranges and what the number on the tube meansWhat Draeger tubes measureStandards and ratings on this page are as published in the documents named and by the manufacturers named. The employer’s hazard assessment and written program decide what applies at a given workplace. Verify a rating on the product and its spec sheet before use.