Are you really sure you want someone to change the setting in a toxic gas detector that determines whether you're notified of a hydrogen sulfide or chlorine gas leak?

At first glance field adjustable settings may seem like a great feature; flexible, modular and easy to do too. But be careful, it may be too easy.

I Can Be Dangerous; and, Stuff Happens

If I'm responsible for the safety of others, I don't want a guy like me to have the ability to change alarm levels. I'm cautious and careful, but occasionally I transpose numbers, or may skip a step in a procedure due to any number of things that are happening on a bad day. That's a dangerous combination with a gas detector.

Beside simple human error, other risks with field adjustment include deliberate tampering, and even worse, settings made by authorized personel with good intentions who don't have a full understanding of a system or instrument.

Things can go wrong so easily and in so many different ways, especially with complex systems. I marvel at how the unlikeliest, once in a life time sequence of events can somehow come together to cause a tragedy. For these reasons and more, you need to minimize the potential for error or malfunction in your gas detector.

You Need Backup

It's important to remember how dangerous these gases are and to be aware of how the body responds to them. Carbon monoxide is colorless, odorless, and tasteless. Overexposure symptoms can be mistaken for food poisoning or the flu. A victim can slip into unconsciousness and away without ever realizing what happened. Our ability to smell some gases can be diminished by prolonged or excessive exposure.

Keep It Simple

Our approach to gas detection at Foxcroft incorporates the KISS principle, Keep It Simple Stupid, coined by engineer Kelly Johnson of Lockheed Martin.

Even though Foxcroft toxic gas detectors include the finest gas sensors available, we've chosen not to provide field adjustable settings or or risk transmission interference with wireless sensors. We've avoided a high level of complexity in operation, installation and calibration to minimize the potential for error.

While we offer "non-standard" operating ranges and custom alarm levels upon request for applications not related to personal safety, we don't make them field adjustable.

Remember what you're trying to do

With more features being developed through rapidly changing technology, we need to remember the purpose of toxic gas detectors: accurate, reliable gas detection and notification, all the time.

Before committing to a detector with adjustable alarm levels or any other "advanced features", determine if they're truly needed for your circumstances or the application. If so, does the detector include a means to prevent improper alarm settings or other human generated errors?  In any event, develop a gas detector protocol that includes plenty of checks and balances.

To maximize your margin of safety, keep it simple to minimize the number of things that can possibly go wrong. The gases you're working with may not give you a second chance. 

 Occasionally we encounter flow reduction or blockage in chlorine analyzers monitoring certain groundwater sources.

We examined this problem at a well station in our area that chlorinates and monitors ground water. The water drawn from the sample tap, unlike aerated "white water", was initially clear with some microbubbles of dissolved oxygen or gases.

These microbubbles decompressed and expanded into clusters of larger bubbles to restrict the orifice in the analyzer flow cell. The blockage would trigger a low chlorine alarm and require extra attention from the operators to remain in compliance.

In our research we found that bubble traps or bubble eliminators can provide mixed results in some applications; so we decided to  prevent bubbles from developing within the analyzer.

Our FX-1000P Rotometer keeps the sample pressurized through the flow cell orifice until it reaches the measuring cell. Since the residual is determined almost instantly, the sample overflows to waste before bubbles have time to enlarge and cause problems. 

The controlled flow also eliminates the need to recalibrate due to flow rate changes, which simplifies consistent, accurate chlorine residual measurement. It's easy to install and includes a pressure regulator with gauge.

So why does our model FX-CLv2 residual chlorine analyzer use ordinary distilled white vinegar and what does it mean for you?

1. It Optimizes Chlorine Residual Readings 

A true on-line, amperometric, chlorine residual analyzer requires a pH buffer to bring the sample pH down to a range where optimum free chlorine residuals can be accurately measured, ideally 4.0 to 4.5 pH.

Any amperometric chlorine residual analyzer that claims buffers are not required uses either a pH buffered electrolyte in the  probe, or makes an electronically simulated pH compensation (which is not a true chlorine residual reading).

The vinegar reduces the pH in the sampling cell, which provides the current potential needed to measure chlorine residuals accurately. Through dissociation, chlorine will be in the measurable form of   hypochlorous acid rather than in its ionic state that can't be measured.

2. DPD Is Toxic, Vinegar Is Better For Our Water & Your Budget

Toxic DPD discharged to waste from one colorimetric chlorine analyzer may not seem like much; until we consider the thousands of colorimeters in service throughout the country.

The impact of toxic DPD discharge is being examined. Minimizing the use of toxic reagents could become even more important as water reuse and recycling increases.

Our contribution is to use a buffer solution, or reagent, that we all consume regularly in various foods. Distilled white vinegar is a food product, and as such doesn't require special haz mat permits or disposal, which is good for your budget and our environment.

3. Do The Math, It's Less Costly

Some chlorine analyzers require expensive, proprietary pH buffer solutions or reagents. In most parts of the country distilled white vinegar costs less than $2.50 per gallon. This means the monthly  reagent cost for an FX-1000P measuring free chlorine is roughly the same price as a large pizza with extra toppings.

4. Cleanliness Is Next To Godliness

This proverb traditionally refers to personal hygiene, but it also applies to the measuring cell of our chlorine analyzer. The vinegar enhances the action of the cleaning balls in the measuring cell. It works to dissolve grease, iron, manganese, dirt and other solids. Cleanliness provides more accurate readings. It also prevents the electrodes from becoming insulated by precipitates or contaminants.

5. In A Pinch It's Readily Available

It seems like things usually break or run out after normal business hours. If your Foxcroft chlorine analyzer runs out of buffer solution at 8 PM Friday night you don't need to take grab samples over the weekend. You can pick up more "buffer solution" at a 24 hour grocery store, convenience store, or in a pinch, from your own kitchen.

"If there's a hole in a sodium hypochlorite truck, the liquid spills on the ground and there's no big toxic cloud. It's what they call an inherently safe technology."

 I read this in an article recently published by The Times-Picayune about the New Orleans Sewerage and Water Board’s plan to switch from using chlorine gas to sodium hypochlorite as its primary disinfectant. The goal is to reduce the risk of a catastrophic chlorine gas leak in neighborhoods surrounding the plant due to either railroad tankcar accidents or terrorist acts.

Risk reduction, especially for densely populated areas, is a smart move.

But statements like this about sodium hypochlorite, commonly referred to as bleach, just make me cringe.

False sense of security surrounding bleach

I feel uneasy because customers have told me that bleach is safe. I’ve read proclamations that the risk of a chlorine gas leak has been eliminated by switching from chlorine gas to bleach.

It’s not. And it hasn’t.

Bleach contains chlorine, treat it with the respect you give chlorine gas

This isn’t about bashing sodium hypochlorite; we need it to keep our water safe to drink. The point is it contains chlorine and needs to be treated with the respect it deserves; the same respect which is given to elemental chlorine gas.

The statistics don’t lie; you still need a gas detector

Given the number of reported incidents of chlorine gas exposure caused by accidentally mixing sodium hypochlorite and acid, we always recommend that a bleach storage area should include a chlorine gas leak detector. It not only helps protect personnel and equipment, it can also help demonstrate that everything possible was done to limit the consequences of an accident.

Sodium hypochlorite can produce the same chlorine gas that's being eliminated

Sodium hypochlorite’s properties and characteristics require careful consideration to ensure disinfection of the process water and safe usage through proper equipment selection, maintenance, and handling.

• Sodium hypochlorite degrades over time, which reduces the amount of available chlorine for disinfection and produces undesirable byproducts.
• Combining bleach with acids can release elemental chlorine gas, the same stuff that’s being eliminated by many treatment plants.
•  Sodium hypochlorite can be explosive if mixed with many organic compounds, including petroleum products such as oils, fuels and grease.  Other toxic and flammable gases can be generated by improper mixing with other chemicals under certain conditions. 
•  Under certain conditions, sodium hypochlorite that has dried on rags or clothes can spontaneously combust. Higher concentrations that dry in heated conditions, such as around pump seals, can become ignitable or explosive on impact.¹

 Be Informed

There are numerous other hazards that users need to consider for safe operation. The Chlorine Institute has a wealth of knowledge regarding chlorine and sodium hypochlorite, including free brochures available for download. If you use bleach, we urge you to check it out here.

A switch from chlorine gas to bleach can reduce the magnitude of a chlorine gas leak. At the same time it switches the type of risks, which requires care to ensure the liquid is used as safely as possible.

I look forward to hearing your view on the subject.

References

1. White’s Handbook of Chlorination and Alternative Disinfectants, 5^th Edition, Black & Vetch Corporation, Hoboken NJ: John Wiley & Sons, Inc. 2010, P 463