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Atmospheric Monitors: “Calibration vs. Bump Testing”

Friday, January 21, 2011

“The fact that we rely on these instruments to detect hazards that may be colorless, odorless, and very often fatal, should be reason enough to motivate us to complete a very strict schedule of instrument calibration/maintenance and pre-use bump testing.”

Here at Roco, we’re often asked for an explanation of the difference between “calibration” and “bump testing” of portable atmospheric monitors. There seems to be some confusion, specifically regarding bump testing. Some folks believe that bump testing and calibration are the same thing. Others think that bump testing is no more than allowing the monitor to run its “auto span function” during the initial startup sequence – or by running a “manual auto span” in order to zero out the display if there is any deviation from the expected values.

To preface this explanation, it is important that the user maintain and operate the monitor in accordance with the manufacturer’s instructions for use. There are some general guidelines that apply to all portable atmospheric monitors and some of the information in this article is drawn from an OSHA Safety and Health Information Bulletin (SHIB) dated 5/4/2004 titled “Verification of Calibration for Direct Reading Portable Gas Monitors.”

Considering that atmospheric hazards account for the majority of confined space fatalities, it is absolutely imperative that the instruments used to detect and quantify the presence of atmospheric hazards be maintained in a reliable and ready state. Environmental factors such as shifts in temperature, humidity, vibration, and rough handling all contribute to inaccurate readings or outright failure of these instruments. Therefore it is critical to perform periodic calibration and pre-use bump testing to ensure the instruments are capable of providing accurate/reliable information to the operator.

Calibration of the monitor involves using a certified calibration gas in accordance with the manufacturer’s instructions. This includes exposing the instrument sensors and allowing the instrument to automatically adjust the readings to coincide with the known concentration of the calibration gas. Or, if necessary, the operator will manually adjust the readings to match the known concentration of the calibration gas.

In addition to using a certified calibration gas appropriate to the sensors being targeted, do not ever use calibration gas that has passed its expiration date. The best practice is to use calibration gas, tubing, flow rate regulators, and adapter hoods provided by the manufacturer of the instrument.

The frequency of calibration should also adhere to the manufacturer’s instructions for use; or, if more frequent, the set protocol of the user’s company or facility. Once the monitor has been calibrated, it is important to maintain a written record of the results including adjustments for calibration drift, excessive maintenance/repairs, or if an instrument is prone to inaccurate readings.

Each day prior to use, the operator should verify the instrument’s accuracy. This can be done by completing a full calibration or running a bump test, also known as a functional test. To perform a bump test, use the same calibration gas and equipment used during the full calibration and expose the instrument to the calibration gas. If the readings displayed are in an acceptable range compared to the concentrations of the calibration gas, then that is verification of instrument accuracy. If the values are not within an acceptable range, then a full calibration must be performed and repairs/replacement completed as necessary.

Modern electro-mechanical direct reading atmospheric monitors have come a long way in recent years in terms of reliability, accuracy, and ease of use. But they are still relatively fragile instruments that need to be handled and maintained with a high degree of care. The fact that we rely on these instruments to detect hazards that may be colorless, odorless, and very often fatal should be reason enough to motivate us to complete a very strict schedule of instrument calibration/maintenance and pre-use bump testing.

For more information on this subject, please refer to the November 20, 2002 ISEA position Statement “Verification of Calibration for Direct Reading Portable Gas Monitors Used In Confined Spaces”; “Are Your Gas Monitors Just expensive Paperweights?” by Joe Sprately, and James MacNeal’s article as it appears in the October 2006 issue of Occupational Safety and Health magazine.
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What does it mean when my atmospheric monitor gives negative or minus readings?

Thursday, December 02, 2010

At some point, most atmospheric monitors will display a “negative” or minus reading for a flammable gas or toxic contaminant. First of all, it is not actually possible for an atmosphere to contain a “negative amount” of a substance. These negative readings usually result from improper use of the monitor.

Most monitors will “Field Zero” or “Fresh Air Calibrate” its sensors when powered on. Because of this, it is very important to power on the unit in a clean, fresh air environment away from confined spaces, running equipment or other possible contaminants. Otherwise, the monitor may falsely calibrate based on the contaminant that is present.For example, a monitor that is powered on in an atmosphere that contains 10 ppm of a contaminant and then moved to fresh air may display a reading of minus 10 ppm. Even more troublesome, if that same monitor is then brought to a confined space that actually contains 25 ppm of the contaminant, it may display a reading of only 15 ppm. As you can see, this could easily lead to the improper selection of PPE for the entrant and result in a confined space emergency.

As always, it is very important to consult with the manufacturer of your particular atmospheric monitor in order to determine how to use it properly. Don’t take any chances with this critical part of preparing for confined space entry or rescue operations.
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Is there a regulation requiring rescuers to use respiratory protection that is “one level higher” than that required for the entrants?

Thursday, November 18, 2010

To our knowledge, there is no regulatory requirement. However, we’ve heard this before and have used it as well when stressing the importance of proper PPE for rescuers, particularly when IDLH atmospheres may be involved. Here’s our thinking… if the entrant’s PPE did not provide adequate protection and he or she is now requiring rescue assistance, then using their “same level of protection” isn’t going to protect you either!

What triggers the use of a greater level of protection? This comes from the rescuer’s assessment of the hazards – including the use of an independent atmospheric monitor from that used by the entrant(s). That’s why it’s so important for the rescue team to provide their own atmospheric monitoring equipment. It also illustrates why written rescue preplans are so important – you need to preplan what equipment and techniques will be required well in advance of an emergency. It’s critical; the PPE selected must be adequate to protect the rescuers.

When preparing rescue preplans, you must also take into consideration any unusual hazards or circumstances that may arise from any work being done inside or near the space. For example, special cleaning solvents might be used or other hazards may be introduced into the space by the workers. Referencing and understanding the MSDS as well as “listening to what your monitor is telling you” are key factors in PPE determination.

OSHA does mention, however, if the atmospheric condition is unknown, then it should be considered IDLH and the use of positive pressure SCBA/SAR must be used. This will protect you from low O2 levels and other inhalation dangers; however, you must also consider LEL/LFL levels. Other factors include non-atmospheric conditions as well. For example, have you considered “skin absorption” hazards and what precautions must be taken?

So, the bottom line, the decision to go with breathing air for rescuers can be determined from your hazard assessment; or, in some cases, by company policy; and even required by OSHA when there’s an unknown atmosphere involved. Remember, it’s much better to be safe than sorry!
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Is a “tailboard briefing” enough prior to a confined space entry?

Monday, November 08, 2010

We had this question from a reader and wanted to post for all to read.

Would a proper tailboard briefing conducted before a confined space entry be sufficient for identifying hazards that may be encountered by the entrants or the rescue team?

It’s true that a tailboard briefing should be an integral part of the larger overall preplanning for a confined space entry. However, well in advance of the entry, a detailed “hazard analysis” of the space should be performed.

A hazard analysis is used to identify the types of hazards, lock-out/tag-out needs, PPE required for entry, method of entry and important rescue considerations. In fact, OSHA requires these written assessments to be completed prior to an entry being made and the confined space permit acts as a secondary written assessment performed at the time of the entry. Here are some OSHA references concerning this topic…

1910.146(c)(5)(ii)(H)
The employer shall verify that the space is safe for entry and that the pre-entry measures required by paragraph (c)(5)(ii) of this section have been taken, through a written certification that contains the date, the location of the space, and the signature of the person providing the certification. The certification shall be made before entry and shall be made available to each employee entering the space or to that employee’s authorized representative.

1910.146(d)(2)
Identify and evaluate the hazards of permit spaces before employees enter them;

1910.146(d)(3)
Develop and implement the means, procedures, and practices necessary for safe permit space entry operations;

The tailboard briefing should be used to confirm or reinforce the information already gathered in the hazard analysis. Because it deals with an individual space at the time of entry, the tailboard briefing is also a very useful tool in finding out if conditions have changed since the hazard analysis was completed.

So, the bottom line… having a detailed hazard analysis for each space that includes a detailed rescue preplan allows a rescue team to review and prepare for potential problems well in advance. Reviewing this information at a tailboard briefing just prior to the entry helps to remind everyone of the possible hazards, the proper precautions, and the potential solutions should an emergency occur.
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Are safety lines required in an actual rescue?

Friday, September 24, 2010

This question was submitted by Thomas Vitti from the Chevron Fire Dept. in Salt Lake City, Utah.

In the event of an actual rescue is a safety line necessary?

Good question… the answer is YES and NO. This question falls into somewhat of a gray area. Much depends on what type of rescue you’re doing; who the safety line is for; and, most importantly, the function of the safety line. Here, we’ve put together our ideas in relation to OSHA regulations, interpretations and our own rescue experience. Then, of course, there’s our motto… “There’s a safe way and a SAFER way,” which we always keep in mind.

Most of the time, the answer for rescuers is YES. Again, one of the most important questions in determining the answer is the function of the safety line during the particular rescue. In most instances, the safety line functions as fall protection, and OSHA requires that all employees be protected from fall hazards. That includes employees performing rescue.

As a rescuer, it is expected that you would be capable of designing a rescue system that maintains two points of contact and meets all fall protection requirements. For example, if you (the rescuer) are being lowered into or out of a space, you would be on a single system (one point of contact) and will therefore need another point of contact (safety line) to act as your second point of contact and fall protection. In this instance, your safety line functions as your fall protection. Once you’ve been lowered to the bottom of a confined space, and you move away from the portal, your safety line then functions as an external retrieval line. However, if it will not contribute to your rescue (or will make it more hazardous), according to OSHA 1910.146, the line is not necessary.

Is a safety line required for the person being rescued (i.e., the victim)? For the most part, YES – it should be part of the preplan for that particular type of rescue. While OSHA requires that all employees be protected from fall hazards, if the patient’s condition is critical (heart attack, suspended unconscious, IDLH atmosphere, etc.) and set-up time for the safety line would cause a delay in getting the proper medical treatment, the rescue team may be justified in not using a safety line for the victim/patient. Additionally, certain circumstances may not require the application of a safety line system for the victim. For instance, if an employee falls and is suspended by a fall arrest system, you don’t need to add another safety line to do the rescue.

Roco’s recommendation…  YES, a safety line is always required for a rescuer – even in a confined space,  where it can also be used for communication purposes. Safety lines for the victim/patient are also highly recommended when the victim will be suspended. But we also realize that there may be life or death circumstances when “quickness of rescue” is more important than the added precaution of using a safety line on the patient. Because Fed OSHA does not specifically address this issue, in certain circumstances, it may be justifiable not to do so.

It is understood that there are unexpected emergency events with many possible mitigating factors to deal with – making it impossible to regulate every potential scenario. So, this leaves some room for judgment based on the circumstances. But if your “justification” is that you did not have sufficiently trained personnel or sufficient equipment to employ a safety line (fall protection) system, OSHA is likely to conclude that you were not properly prepared to perform rescue for your particular work environment.

OSHA does not dictate how a rescue is to be performed. OSHA’s only performance standard for a rescue team is that they are capable of performing rescues in a safe, efficient and timely manner. That’s why we emphasize preplanning, preparing and practicing for the most likely scenarios at your site. Rescue preplans allow teams to plan for safe, effective rescue systems that would include fall protection as part of the plan – in fact, the safety line system could be pre-rigged, bagged and ready to go. The importance of preplanning for rescue is also addressed in OSHA 1910.146(k)(1)(v), which refers to providing the rescue team or service selected with access to all permit spaces from which rescue may be necessary so that the rescue service can develop appropriate rescue plans and practice rescue operations. (Of course, “representative spaces” are also acceptable.)

As a final note, where OSHA does not have a specific regulation that addresses a particular hazard or means of protection, it may cite an employer for violating the General Duty clause – which requires an employer to provide a workplace free of recognized hazards. In citing under the General Duty clause, OSHA can reference national consensus standards, such as ANSI and NFPA, to establish a recognized hazard and acceptable means of protection. These consensus standards can also be invaluable resources for compliance guidance.

Note: It is always important to follow your company’s policies and procedures concerning emergency response operations as well as all relevant standards and regulations for your industry.
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