Atmospheric Monitors May NOT Detect All Dangers

Tuesday, February 09, 2016

By Dennis O’Connell, Roco Director of Training with contributing author Spencer Pizzani of Weston Solutions

Readings are 20.9/0/0/0…so it must be safe for entry, right? Not necessarily! 

Atmospheric Monitors May NOT Detect All Dangers

After completing an interesting confined space standby job for Roco, I wanted to caution rescuers about the possibilities of atmospheric hazards within a confined space – despite what the atmospheric monitor says!

For this particular job, the atmosphere in the workspace never varied on the 4-gas monitor readings. The readings were consistently 20.9% for O2; 0 for LEL; 0 for H2S; and 0 for CO. However, this entry required the use of air-purifying respirators even though there were no visible signs of anything unusual – no odor, no product warning signs, no indication that there may be an inhalation hazard in the space.

This particular space was located at a public water facility. It was a 70-ft. deep concrete metering pit with six consecutive 12-ft x10-ft levels. It had concrete floors and walls with a vertical ladder that accessed each level. Although the space was not designed to store any product, in this case, we still had an atmospheric hazard.

Atmospheric Monitors May NOT Detect All DangersThe purpose of the entry was for remediation of mercury contamination on the concrete surface. The gross cleanup of liquid mercury had been performed years prior, but further action was required to eliminate vapor hazards still present in the lower chambers.

During the first phases of the entry, vapor levels that exceeded 40,000 ng/m3 (nano-grams per cubic meter) were detected. The more frequently updated ACGIH Threshold Limit Value is only 25,000 ng/m3. The work environment in this space routinely approached twice this level, even though there were no visible signs of liquid mercury. The source of the toxic atmospheric hazard was invisible and odorless – mercury vaporizing from the concrete surfaces.

Mercury is only one example of a toxicant that can produce a hazardous atmosphere in confined spaces that will not be indicated on a typical 4-gas meter or atmospheric monitor. Many rescuers assume that their 4-gas meter will detect all atmospheric conditions that may present a risk to their health or safety, but this is just not true. There are a wide variety of agents or toxicants besides mercury that will not be detected and whose presence may require other controls or the use of respiratory protection. This mistake could be deadly, or leave rescuers with chronic health issues.

In this scenario, for example, if you were an off-site rescuer responding to the above described space in an emergency situation. Without someone on site to inform you of the possible hazard, you would have no indication that any hazards were present. Many times as municipal rescuers we respond to, shall we say, shady locations where unauthorized storage or illegal dumping of hazardous products has taken place; there are no SDS, placards, or signage. Personnel on scene may not know, or may not want to relay vital information about a space of any products within the space.

Atmospheric Monitors May NOT Detect All DangersRescuers Beware: It's important to play the role of “detective” when planning or preparing to make a confined space entry.

Oftentimes, there are placards or signs on tanks or storage containers to start the investigation into what hazards may be present – and SDS for additional information. However, as rescuers we often fall into a state of “false security” with our 4-gas meter readings.

While much of our training may include “Go/No Go” scenarios for rescue teams, the use of respiratory protection is usually based on one of the “Big 4” readings on our atmospheric monitors. Unfortunately, this may only serve to reinforce the notion that a 4-gas monitor will always provide the “complete” information of what may be going on inside a confined space. We get dependent on these monitors to tell us if it’s safe to enter without respiratory protection – and there may be much more to the story!

OSHA’s Respiratory Standard [1910.134 (d)(1)(III)] specifies "Where the employer cannot identify or reasonably estimate the employee exposure, the employer shall consider the atmosphere to be IDLH.” 

In the above statement, if you substitute Team Leader for “employer” and “Rescue Team” for employee, you may find that you cannot “identify or reasonably estimate the employee exposure.” Therefore, rescuers would need to use SCBA/SAR and other PPE until you can completely identify what hazards are in the space even though typical monitoring devices are telling us that all is well.

 

Atmospheric Monitors May NOT Detect All DangersWhile your standard 4-gas meter is an important screening tool – it is NOT a "catch all" for every atmospheric hazard.

Remember that NIOSH statistics indicate that 40%-60% of confined space entry fatalities are (would-be) rescuers, including both dedicated on-site standby teams and off-site professional rescuers (municipalities) who attempt to perform a confined space rescues.

But let’s take this a step further. If you ask most rescuers at what O2 level does an atmosphere become dangerous, they will say below 19.5%. I know from my initial hazmat/confined space training on 4-gas monitors included oxygen displacement. It was so elegantly described to me as “if your monitor shows a decrease in oxygen, it is telling you that something else has pushed out that percentage of oxygen and replaced it with some other agent.” Now, it would be up to you to figure out what else is in the air.

For example, normal breathing air is 20.9%. To get a reading of 19.5% means that about 1.4% of “something else” has displaced the oxygen. Then, depending on what that “something else” is, could require the use of respiratory protection. Hey, wait, the good news keeps coming, and I am getting in way over my head on this science stuff, but my high school chemistry teacher should still be proud. Ambient air is made up of about 79% nitrogen and other gases and 21% oxygen. So, using fingers and toes mathematics, that equals about a 4:1 ratio of nitrogen to oxygen.

In other words, if we have a 1% displacement of oxygen from the breathing air, it will be accompanied by about a 4% displacement of nitrogen (both gases displace at about the same rate). Therefore, instead of it being about a 1.4% percent of an unknown product in our breathing air, it could be as much as 5.6% or more! And, depending on what that product is, it could already be at its IDLH level.


Project Scientist Spencer Pizzani of Weston Solutions provides this insight.

"While many rescuers are habituated to only watch oxygen (O2) percent composition, this can be deceptive. The OSHA standard for O2 concentration is based on standard temperatures and pressures at sea level. When an environment presents lower pressure (such as at higher altitudes or in chambers subject to continuous air evacuation), the partial pressure of O2 is decreased as described by the Ideal Gas Law. This can lead to 'normal’ concentrations, but with less oxygen available for respiration.

A widely used example demonstrates that the partial pressure of oxygen in a confined space at high altitudes such as in mountainous areas would be the equivalent partial pressure of 14-15% oxygen at sea level. This can be low enough for the leading effects of asphyxiation to manifest – a problem exacerbated by the high oxygen demand of strenuous rescue work.

Gases that displace oxygen can have a similar effect. A typical 4-gas meter will only read oxygen concentration. This neglects the largest component of ambient air – nitrogen. The portion of air normally occupied by nitrogen is also replaced by another gas. When taken as a whole, the contaminant gasses may exceed levels and require the use of respiratory protection, with no indication from the typical 4-gas meter. Many toxic gases are odorless and colorless. Radiation can be a similar risk. While some types of radiation can be filtered or excluded with the use of respiratory protection, exposure to other types are simply a function of time, distance and shielding. Rescuers entering confined spaces may have a strict time limit for operations as established by a health physicist. In such cases, a 4-gas meter would be entirely unresponsive even in the presence of an instantly lethal radiation exposure vector.”

Pizzani advises,

“Rescuers responding to an emergency always need to look at the big picture and be part detective in identifying potential hazards that may impact both initial and rescue entry. Identification of past residues in storage containers, examination of process system SDS, and any information/knowledge provided by workers familiar with the space or process is invaluable. Warning signs such as odors, visible dust, or any variability on oxygen concentration should be met with a thorough set of instrument diagnostics and further investigation.”

Summary

A standard 4-gas meter is an important screening tool for atmospheric acceptability. However, it is "not a catch all" for every atmospheric hazard. Developing a detailed preplan; identifying possible hazards; and proper PPE should be the top priority of anyone planning a rescue entry. The use of supplied air systems (SAR/SCBA) should be considered “minimum protection” for rescuers until an atmosphere is completely characterized or in the event of an unknown agent or condition. Remember, a standard 4-gas meter may not be telling the whole story.

Special thanks to contributing author, Spencer Pizzani, who is an Industrial Hygienist and Project Scientist for Weston Solutions, Inc. Weston is a global environmental consulting firm specializing in environmental solutions, specialty construction and green development.

read more

INVISIBLE HAZARD KILLS AGAIN

Wednesday, January 18, 2012

INVISIBLE HAZARD KILLS AGAINRoco Director of Training/Chief Instructor, Dennis O’Connell reviews the importance of following OSHA safety standards for confined space entry, no matter how many times workers have entered the space. The take away? With confined spaces…It’s NEVER old hat! The importance of preplanning confined space entries and identifying “potential hazards ”should be old hat by now. Yet every year we are still killing entrants and rescuers in confined spaces.

In the story below, we have one very lucky rescuer, but this very easily could have been a multi-fatality event.

Atmospheric Hazards Continue to Claim Lives in Confined Space Entry Scenarios

INVISIBLE HAZARD KILLS AGAINThe importance of preplanning confined space entries and identifying “potential hazards” should be old hat by now. Yet every year we are still killing entrants and rescuers inconfined spaces.  In the story below, we have one very lucky rescuer, but this very easily could have been a multi-fatality event.

It’s always important to remember that each entry stands alone. Each and every time a space is entered, we need to:

(a) identify potential hazards;

(b) eliminate or control them, when possible;

(c) use proper PPE; and,

(d) have an EFFECTIVE Rescue Plan.

Otherwise, as in this story, we will lose or injure workers as well as those attempting the rescue.

Start from scratch and treat each entry like it’s the first time you’re entering the space – it could save your life.

Keep in mind, the history of a space really has nothing to do with the current entry. We’ve all heard people say, “We do this all the time, and we’ve never had a problem!” Or, “We’ve entered this space a thousand times and the air is always good!” Remember this… IT DOES NOT MATTER!! This entry has nothing to do with the last.

As you read of yet another unfortunate incident, let it be a reminder to those of us who make entries or do rescues from confined spaces – do not let your guard down, do not get complacent…it could be deadly. Atmospheric hazards are still one of the leading ways that people are dying in confined spaces. Because humans are visually oriented by nature, if we can see a hazard, we’ll protect ourselves from it. However, if we can’t see it, we tend to assume it’s safe. OSHA’s 1910.146 PRCS standard and others were developed for a reason… people were making tragic mistakes and dying in confined spaces. These standards and guidelines are written so we don’t make the same mistakes.

OSHA FINES UTILITY FIRM $118,580 FOLLOWING WORKER’S DEATH

INVISIBLE HAZARD KILLS AGAINOSHA has cited a contracting and utilities company for two willful and two serious safety and health violations following the death of a worker at the company’s Texas facility. Proposed penalties total $118,580. An inspection was initiated by OSHA on June 28 in response to a report that employees working on a new sewer line were exposed to inhalation of a hazardous chemical. One employee who entered a manhole to remove a plug in order to flush out accumulated debris became overwhelmed by toxic fumes and died. Another employee was hospitalized after attempting to rescue his co-worker.

The willful violations are for failing to test for atmospheric conditions and provide adequate ventilation and emergency retrieval equipment prior to entry into a manhole.

The serious violations are failing to provide or require the use of respirators as well as conduct an assessment to determine the potential for a hazardous atmosphere where oxygen deficiency, methane, and/or hydrogen sulfide were present or likely to be present.

“The company failed to ensure that proper confined space entry procedures were followed,” said Jack Rector, OSHA’s area director in Fort Worth. “If it had followed OSHA’s safety standards, it is possible that this tragic incident could have been prevented.”
read more

Atmospheric Monitors: “Calibration vs. Bump Testing”

Friday, January 21, 2011

Atmospheric Monitors: “Calibration vs. Bump Testing”“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.
read more

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.
read more

How much training is needed for attendants on air monitoring equipment?

Wednesday, September 01, 2010

Reader Jeff Machen had a question concerning how much training to give attendants on air monitoring equipment; especially when they may only be working a week long shut down? Here’s our reply from CSRT Manager Bryan Rogers.

When you’re dealing with temporary labor, it is difficult to ensure that they are well trained on something as complex as atmospheric monitoring. We checked with several equipment manufacturers, and they don’t set a specific amount of training required, but leave it up to the customer’s internal company policy and/or person(s) issuing the monitor.

We also spoke to a few of our instructors who work at different plants and refineries. The majority of these companies require a company employee to perform the initial monitoring and then again after a break in work greater than 30 minutes. In addition, they review with the attendant what to look for and what to do if there are changes in the readings or an alarm sounds. One company provides a four-hour PowerPoint presentation on monitoring and attendant responsibilities.

OSHA does not indicate a time frame for this training either. However, it does require that persons be capable of safely performing the tasks assigned. Therefore, I would say your best bet would be to cover as much of the manufacturer’s instructions as possible along with reviewing the most common problems such as…

    - Calibration conversions
    - Turning on the monitor (or “field zeroing”) in the presence of contaminates
    - Negative LEL or negative toxic readings
    - Contaminated sampling hoses
    - Clogged filters

Lastly, I would stress to the attendants the importance of contacting a supervisor if they have any questions or concerns - and, if they get any unusual results from the monitor… “Do not hesitate to have everyone exit the space while the results are investigated!”
read more

RescueTalk (RocoRescue.com) has been created as a free resource for sharing insightful information, news, views and commentary for our students and others who are interested in technical rope rescue. Therefore, we make no representations as to accuracy, completeness, or suitability of any information and are not liable for any errors, omissions, or delays in this information or any losses, injuries, or damages arising from its display or use. All information is provided on an as-is basis. Users and readers are 100% responsible for their own actions in every situation. Information presented on this website in no way replaces proper training!