All gas monitors need to be bump tested, even if they don’t require calibration. (Yes, that goes for you guys with single gas disposable monitors too.) To test your monitor you’re going to need both calibration gas and a regulator. Your calibration gas mixture will be determined by the type of sensors in your gas monitor. Your regulator will have to fit your bottle of gas. Problem is there are a couple of different types of regulators, and it’s not very intuitive figuring out which you’ll need.
Let’s start with the most basic regulator. A constant flow regulator is designed to work with diffusion instruments like the simple GasAlert Clip Extreme H2S Monitor, but works just fine to test a monitor with an internal pump. A constant flow regulator simply screws onto the top of the cylinder. Tygon tubing is attached to the testing clip and the monitor on one end and the regulator nipple on the bottle. This set-up provides an on/off knob to get the the gas out of the bottle. This most basic of gas delivery systems provides a specified flow rate of gas when it’s open (typically 0.5 or 1.0 liters per minute, but we sell the 0.5 far more often).
We’re clear on what diffusion means, right? The sensors measure only the gas they come in contact with. There is no sample pump on a diffusion monitor. 4-gas diffusion monitors are often worn by workers while they are working in a confined space. Single gas diffusion monitors like the GasAlert Clip from BW are used around oil and gas production facilities where a specified gas is sometimes present.
Keep slogging along with me here! The type of gas you use will have an effect on the type of regulator you need. For example, gases like hydrogen sulfide, chlorine, ammonia all all reactive. They will interact with the material of a steel cylinder and corrupt their concentrations. These reactive gases need to be kept in a non-reactive container like aluminum. Aluminum and steel cylinders have different threading. Steel has a male thread, while aluminum cylinders have a female thread. Is there some kind of social commentary here? No, it’s just the way it is.
At PK Safety, we sell more 4-gas Calibration Mixes than anything. Since the 4-gas mix includes H2S, it comes in an aluminum cylinder. A diffusion-style monitor is going to need the constant flow regulator we mentioned earlier. And since we know the cylinder is aluminum, and therefore has female threads, we need a regulator with male threads.
I can’t believe it took me four paragraphs to spit that out.
Let’s keep going. A demand flow regulator has an internal switch that allows gas to flow when there is a pull against it. Demand flow regulators are used with gas monitors with an internal sample pump like the RKI Instruments GX-2012. By following the manufacturer’s instructions on bump testing and calibration, your monitor will use only the gas it needs to affect the sensors.
Because gas is quite expensive, the demand flow regulators, and their limited gas consumption, help to save money.
I’m going to confuse the issue just a bit here and mention that while many calibration stations require separate regulators, there is at least one option out there – the Draeger X-am 4-Gas Monitor and Bump Test and Calibration Station that simply requires you to screw in your cal gas and plug in your monitor. This is the exception to the rule, and many systems require you to buy these parts separately.
Summary for ALL MAKES of gas monitors:
Diffusion monitor testing with non-reactive gas only (methane, isobutylene, carbon monoxide, etc.) – constant flow regulator, female threads.
Diffusion monitor testing with reactive gas (including 4-gas monitors testing H2S) – constant flow regulator, male threads.
Monitor with internal pump testing with non-reactive gas only (methane, isobutylene, carbon monoxide, etc.) – constant flow regulator, female threads.
Monitor with internal pump testing with reactive gas (including 4-gas monitors testing H2S) – demand flow regulator, male threads
There you are. Clear as a dark, confined space.
You can always just call us at 1-800-829-9580 or contact us online at www.pksafety.com. We’re happy to look up the manufacturer, and let you know which regulator you need.