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Pre-entry Atmospheric Clearance Measurements

Friday, March 17, 2017

The following article was written by Russell Warn and published in ISHN magazine (ishn.com), December 2016. Roco comments have been added to the article and are noted in red.

Working in confined spaces presents a unique and dangerous challenge in combatting the unseen – oxygen deficiency, poisonous or explosive gases, and other hazardous substances are among the most frequent causes of accidents associated with work in confined spaces and containers.

From 2005-2009, the Bureau of Labor Statistics reported nearly two deaths per week, or roughly 96 per year, could be attributed to confined space, with about 61 percent occurring during construction repair or cleaning activities.

With conditions subject to change in a moment’s notice, taking steps to protect against life-threatening dangers should always be a top priority in confined spaces. Performing a thorough clearance measurement is a demanding — yet crucial — task that dictates the safety environment, and should not be taken lightly. To help guide you along your road to enhanced safety, outlined below are several best practices based on frequently asked questions.

When should I perform a clearance measurement?

Conduct clearance measurements immediately before operations begin. Environmental factors such as temperature and air flow can change the atmosphere, causing readings to fluctuate. One shift’s measurement taken at 7 a.m. is not representative of the conditions when work operations commence for another shift at 4 p.m. New clearance measurements must be taken immediately to account for the nine hours of changing temperatures and ventilation patterns, depicting the accurate readings of present conditions.

Roco Comment: In addition to pre-entry clearance measurements, entry into permit spaces during construction activities requires "continuous atmospheric monitoring" unless the entry employer can demonstrate that equipment for continuous monitoring is not commercially available or periodic monitoring is sufficient. Ref. 1926.1203 (e)(2)(vi), 1926.1204 (e)1)(ii), and 1926.1204 (e)(2). Additionally, Roco believes that for "ALL" permit entry operations, it is advisable to provide continuous atmospheric monitoring no matter what the industry activity entails.

What’s the importance of zero-point adjustment?

When performing clearance measurements, it’s crucial to determine the reference point of the gas detector by calibrating the zero-point. The zero-point ensures that the indicated values correspond to the actual existing gas concentrations. In order to determine that the actual zero-point has been found, calibrate equipment in an environment where the hazardous substance is not present, such as fresh air environments. With every scientific test, no matter the field, a control group, which serves as a starting point of reference, permits for the comparison of results to show any contrasting changes. The zero-point calibration acts as such, allowing workers to identify the presence, or lack thereof, of different gas concentrations.

Where do I measure/take the sample?

When it comes to measuring samples, there are four things to keep in mind: the physical properties of gases, and the type and shape, temperature and ventilation patterns of the confined space.

Know the differences between light and heavy gases. Clearance measurement experts must have a strong working knowledge of hazardous substances’ properties, as they play a role in where measurements should be taken. For example, if a sample is pulled from the top of the confined space and hydrogen sulfide (H2S) is detected, the sample may not be entirely reliable. H2S has a molar mass of 34 g/mol, which is significantly heavier than that of air (29 g/mol). As a result, H2S sinks to the bottom of a space, where its concentration would be greatest. Identifying a presence at the top of the confined space says immediate danger and appropriate actions should be taken.

Light gases quickly mix with air and rise to the top. As a result, any measurements in open atmospheres should be performed close to the leak, and increases in concentration should appear in the highest points of the confined space. Heavy gases, on the other hand, should sink and flow like liquids, pass obstacles or stick to them. They barely mix with air like light gases do, so their samples should always be taken at the lowest points of the confined space.

Determine the type/shape of the confined space: In an ideal scenario, each confined space area would be in an “even” or level position. This isn’t always the case, and a container may be placed on an inclined surface, making the highest point in the corner positioned toward the top of the inclined surface. Thus, entry may be nearer to where the heavy gases have accumulated.

Take tabs on temperatures. All matter is made up of atoms and molecules that are constantly moving. When heat is added to a substance, such as a gas, the molecules and atoms vibrate faster. As the gas molecules begin to move faster, the speed of diffusion increases. If the sun has been shining on a tank for hours, there’s a good chance the clearance measurement taken at dawn no longer reflects the current readings due to the increase in diffusion.

Vet the ventilation. Air currents change the position and concentration of air clouds, and often times, the way a confined space is ventilated can affect readings. Containers cannot always be separated from pipelines, or there may be leaks in the tanks that must be accounted.

Roco Comment: Not only is it required by certain OSHA provisions like alternate entry procedures, but Roco highly recommends monitoring the atmosphere prior to initiating ventilation. This is intended to provide a reasonable assessment of the potential atmosphere change should the ventilation equipment fail. The rate for a potential hazard to re-develop will be based on factors such as the effectiveness of isolation, any residual product within the space, temperature, humidity and passive ventilation which are among just some of the factors.

How do I safely conduct the measurement for an accurate reading?

People often question why they can’t just use the carrying strap of their device to lower the device into the confined space for a reading. Although this seems like a simple fix, it’s not a safe or recommended way to conduct the measurement. Lowering the device into the container this way not only obscures the way the display is read, but it may not audibly alarm. If the measured value is slightly below the threshold value and the alarm does not sound, a worker would not be notified of the dangerous concentrations lurking below. Not only this, but measurements may be inaccurate since the measured gases, due to their molar masses, may be concentrated at a higher or lower point within the container. Clearance measurements should be conducted on-site and on-the-ground of the confined space for accurate, safe readings.

Roco Comment: The points made in the preceding paragraph are certainly valid. The best solution that we can offer is to use remote sampling probes or tubes to actively draw (pump) samples from the stratified levels of the space while the direct reading instrument is in a position outside the space to observe the real time readings. To expound upon the point the author makes, if the pre-set threshold for the alarms are not enough to trigger the alarm indicating the presence of a hazardous atmosphere, and the individual performing the assessment relies instead on rapidly pulling the monitor from the space in the hope that they are able to read the display before the values change, is a very dangerous way of approaching this procedure. Depending on the sampling rate of the monitor, the hazardous gas(s) may have cleared from the monitor in the time it takes to withdraw it from the space, and it is very likely that the instrument will display a normal atmosphere by the time it is back within view. Additionally, for areas within the space that cannot be remotely assessed by remote sampling prior to entry, the only safe recourse is to limit entry to the areas that have been assessed and to take a monitor into the space to continuously assess the unreachable regions before venturing further.

What do I need to document during clearance measurement protocols?

Just as it’s important to remain thorough in clearance measurements procedures, it’s equally as important to remain thorough in the general housekeeping protocols surrounding samples. This includes documenting:

  • The container number
  • The measuring point of the container, and whether there was more than one measuring point
  • At which time was the clearance performed
  • Under what condition was the measurement performed
  • Measured hazardous substances
  • Name of person performing measurement
  • Equipment used for clearance

Safety, regardless of job title or responsibility, should be everyone’s top priority. When working in the midst of poisonous and explosive hazards, performing clearance measurements correctly and carefully means not only keeping one’s self safe, but keeping the working environment safe, as well.

About the Author:
Russell Warn is the product support manager for gas detection products at Dräger. He has been in the safety industry for more than 29 years, with most of this time dedicated to gas detection product and application support.

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Q&A: Fall Pro Recert

Wednesday, June 01, 2016

READER QUESTION:
I went through competent person for fall protection several years ago and since that time a lot has changed regarding the types of fall protection equipment and systems that are available. Should I get update training for this role?

ROCO TECH PANEL ANSWER:
Yes, definitely. In fact, ANSI Z359.2 states competent person training update training shall be conducted at least every two years. It is always a great idea for competent persons to stay abreast of not only any legislative changes, but also to stay current on consensus standards such as ANSI, and certainly on emerging equipment technologies. It is amazing how quickly new fall protection equipment is becoming available. It wasn’t long ago that harness mount self-retracting lanyards were just a drawing on an engineer’s desk, and now there are so many different versions it is mind boggling. OSHA’s recognition of suspension trauma as a workplace hazard to fallen suspended authorized persons has created an entire market segment for systems to help deal with this hazard. So receiving update training for this crucial role at least every two years is certainly a great idea.

READER QUESTION:
Can I complete competent person for fall protection training via an on-line course?

ROCO TECH PANEL ANSWER:
We discourage that type of course other than for learning the legislated requirements. There just is no substitute for hands-on training. One of the most important responsibilities of a competent person for fall protection is the performance of periodic equipment inspections. I can’t imagine having any way to show competency of this skill without demonstrating it to a live instructor/evaluator.

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What is a Competent Person?

Wednesday, March 02, 2016

Many OSHA standards, especially in construction, require a “competent person” to be designated at the jobsite. Filling this role requires proper training, relevant experience to the work being performed and adequate knowledge of the associated regulations. 

The competent person should be able to recognize critical hazards as well as have the authority to take the action needed to mitigate hazards. It’s much more than just picking someone to fill a slot.

A previous article, "What is a Competent Person?" found in the National Safety Council's Safety+Health publication, talks about how the term is often taken too lightly. Again, it's much more than just selecting a body to fill a role or attending one 10-hour training class covering all the various standards. Competency must be considered and evaluated for this important role. 

At a minimum, your designated competent person should meet the following minimum qualifications:
(1)    A high level of understanding of the types of hazards typically encountered in that area of work;
(2)    A solid review of applicable standards relating to that type of work; and,
(3)    A thorough understanding of types of solutions to control or eliminate the hazards
.

To assist in preparing your competent person in fall protection, we encourage you to register for Roco's Fall Protection
Competent Person - April 4-5, 2016 course in Baton Rouge. This course will provide practical experience in recognizing fall hazards and developing appropriate measures for reducing or eliminating those hazards. 

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Q&A: What are the Rescue Requirements for Trenches/Excavations?

Tuesday, May 19, 2015

READER QUESTION:
One of our readers recently asked about rescue requirements in excavations. We did some searching and found an interesting Letter of Interpretation (LOI) from OSHA that explains when rescue provisions are required during trenching operations.  

ROCO TECH PANEL ANSWER:
The following is from OSHA LOI in regards to this answer. In regard to whether emergency rescue equipment is required at every trenching job site located near or passing by a gas station, refinery, gas line, sewer main, etc., please be advised by the following:

Emergency rescue equipment is required to be readily available where a competent person determines, based on the conditions at each job site, that hazardous atmospheric conditions exist or may reasonably be expected to develop during work in an excavation. In regard to whether a contractor can rely on a local rescue squad instead of providing the rescue equipment, please be advised that many emergency situations associated with the hazards involved with hazardous atmospheres in trenches would normally require an immediate response within a few minutes or even seconds. A rescue squad would be unable to provide the necessary response and therefore could not be used to comply with 1926.651(g)(2).

As more and more industrial sites realize that just about every day, somewhere on their property, there is an open trench. Trench collapses cause dozens of fatalities and hundreds of injuries each year. Obviously, this creates concerns, especially for the rescue personnel who may be called to the scene during an emergency.

We’ve been getting questions from clients that have effective rescue teams for medical, hazmat, fire, confined space and rope but are realizing that they are lacking if a trench collapse occurs on their site. “Who will do the rescue?” is a question often asked. There is concern by supervisors, who have been given the responsibility for signing trench permits, but have not had adequate training in trench and excavations. Many are not “competent persons” as referenced in OSHA1926.651-652.

After looking at the dozen of questions in the referenced LOI, it should raise a few more:

  1. Are the people you have signing off that a trench is constructed properly and safe for entry, trained to know what to look for and have the authority to act (competent person), or are they assuming that the contractor is “doing the right thing”?
  2. Who will be called if a trench emergency should occur?
  3. Are their local resources that have the training and equipment to respond, or are you an island unto yourself when it comes to trench rescue? 

The link to the referenced LOI is shown below – and the questions are still very relevant : https://www.osha.gov/pls/oshaweb/owadisp.show_document?p_table=INTERPRETATIONS&p_id=20597

Additional Resources:

OSHA Technical Manual

OSHA Trenching and Excavation Safety

Trench Safety Poster – An Unprotected Trench Is An Early Grave

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Roco Tech Panel Q&A - Prompt Rescue by Shift

Sunday, February 01, 2015

READER QUESTION:
Our company procedures require an on-site rescue capability for permit- required confined space entry operations during normal Monday-Friday “day shift” operations, but for entries other than during that shift, we rely on an off-site rescue service. Shouldn’t the rescue capability, specifically the rescue response time, be the same no matter when the permit required confined space entries are being made?

ROCO TECH PANEL ANSWER:
Yes; and no, not necessarily.

Yes, if the nature of any known or potential hazards that may affect the entrants in the permit space, and the configuration of the confined space are the same during regular M-F day shift as they would be during off-shift entries, then the answer is yes. The rescue capability regarding response time, manning, equipment, and overall performance capability should be the same.

No, not necessarily. For example, if the nature of the known or potential hazards of a permit space entered during the day shift requires a shorter response time, or if the configuration of the space requires a higher level of rescue expertise, rescuer PPE, number of rescue personnel, or if there is any other factor that may require a different performance capability than the requirements of the day shift entries, then no, the same rescue capability would not necessarily be required.

This is because OSHA 1910.146 is a performance-based standard. For confined space rescue, specifically regarding what would be considered “prompt rescue,” the performance standard will be most influenced by the nature of the potential and known hazards and how quickly the hazards will affect the authorized entrants, as well as the complexity of providing effective rescue from the particular permit-required confined space.

To demonstrate this point, here are some extracts from OSHA 1910.146 Permit Required Confined Space Regulation Section K, the Summary and Explanation of the Final Rule, and also from OSHA 1910.146 Appendix F.

From 1910.146 (k)(1)(i)“Evaluate a prospective rescuer's ability to respond to a rescue summons in a timely manner, considering the hazard(s) identified;

Note to paragraph (k)(1)(i): What will be considered timely will vary according to the specific hazards involved in each entry. For example, §1910.134, Respiratory Protection, requires that employers provide a standby person or persons capable of immediate action to rescue employee(s) wearing respiratory protection while in work areas defined as IDLH atmospheres.”

From the Summary and Explanation of the Final Rule (1910.146) “OSHA has therefore decided to promulgate the requirement it proposed for "timely" rescue, a requirement that was not opposed by any rulemaking participant, rather than to define precisely what is timely. That determination will be based on the particular circumstances and hazards of each confined space, circumstances and hazards which the employer must take into account in developing a rescue plan. OSHA has added a note to paragraph (k)(1)(i) to clarify this point.”

From 1910.146 Appendix F, A. Initial Evaluation, II, 1. “What are the needs of the employer with regard to response time (time for the rescue service to receive notification, arrive at the scene, and set up and be ready for entry)? For example, if entry is to be made into an IDLH atmosphere, or into a space that can quickly develop an IDLH atmosphere (if ventilation fails or for other reasons), the rescue team or service would need to be standing by at the permit space. On the other hand, if the danger to entrants is restricted to mechanical hazards that would cause injuries (e.g., broken bones, abrasions) a response time of 10 or 15 minutes might be adequate.”

The response time of the rescue service is also different than the time needed to provide rescue. Response time generally means the time it takes for the rescue service to arrive on scene. From that time forward, the rescue service must perform a size-up, identify and don PPE, set up rescue systems, and perform many other tasks before initiating entry rescue. Any need to provide victim packaging or to deliver breathing air to the victim will add to the total time it takes to complete the rescue.

Therefore, it is imperative that the employer ensures that the measure of “Prompt Rescue” is driven by the nature of the known or potential hazards of the permitted confined space as well as the complexities of the configuration of the space and how those will effect the time required to the setup the rescue system.

Roco provides confined space rescue services for a variety of industries and is confronted with a very wide range of hazards associated with the entry operations and a vast range of space configurations. The determination on the rescue team’s posture is based primarily on the answer to the following questions.

  • 1.  How quickly will the entrants be overcome by the known or potential hazard(s) of the space, and /or how quickly will the entrants suffer permanent injury if exposed to those hazards?

  • 2.  If non-entry retrieval systems are not employed due to the system not contributing to an effective rescue, or the retrieval system creates a greater hazard, how much time would be needed to arrive on scene, set up an entry rescue system to support the entrant rescuer(s) and the victim(s)?

These are just two of the primary questions that we consider for our CSRT operations. If the nature of the known or potential hazards would require a near immediate rescue of the entrant(s), we would assume a “Rescue Standby” posture where the rescue systems are pre-rigged, the entrant rescuers are already in appropriate PPE or have it available to be quickly donned, and the rescue effort can be initiated in a very short time in an effort to meet that “Prompt Rescue” performance benchmark.

It is vitally important that the employer honestly evaluates the nature of the hazards or potential hazards of the permitted confined spaces that they plan on entering. This can be accomplished by reviewing product SDS (Safety Data Sheets), understanding the nature of the hazards that are not included in the SDS, and always considering worst case scenarios. Additionally, the employer must include an evaluation of the time it would take the rescue service to arrive on scene as well as the additional time to safely assess the situation and setup the required rescue systems prior to initiating rescue.

The answer to the question of a different rescue capabilities based on the “day shift” or “night shift/week-ends” can only be answered by performing a thorough assessment of the permitted spaces. And, on a case by case basis, determine if the rescue capability for that particular entry operation does indeed meet the spirit of “Prompt Rescue.” 

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