Confined Spaces: Myths, Magic, Urban Legends and the Facts

Much of the “popular” information circulating about confined spaces is simply wrong. Confined spaces don’t have to be labeled. Oxygen levels of 19.5 percent aren’t necessarily “safe” for entry. The mere possibility that an atmospheric hazard may exist doesn’t necessarily mean that a confined space is a permit space. Showing employees a 20-minute video or sending them to a one-day, state-sponsored fire rescue institute seminar doesn’t mean they have been trained.

Much of the truth underlying these myths can be found by carefully reading the OSHA standard, its preamble, the related compliance directive and the more than 80 formal letters of interpretation concerning confined spaces that the agency has issued over the last decade.

Myth: The OSHA standard requires you to prepare a written inventory of permit-required confined spaces.

Fact: Read 29 CFR 1910.146(c)(1). It only requires you to “… evaluate the workplace to determine if any spaces are permit-required confined spaces.” While conducting an inventory is one way of doing this, it’s not the only way. If you know your facility well enough, you might be able to make an evaluation without leaving your office. Don’t believe me, look at the answer to the third question in Appendix E, section (c) of CPL 2.100.

Once you’ve identified your permit spaces, you must inform your employees about the existence of these spaces and of the hazards they pose. This leads to another confined space myth — that permit spaces must be labeled.

Labeling Myth

Myth: The standard requires that permit-required confined spaces be labeled or posted.

Fact: If you read 29 CFR 1910.146(c)(2), you will see that the standard requires that employees be informed of the existence, location and danger posed by permit spaces” … by posting danger signs or other equally effective means” [emphasis added] In other words, you can explain to people what a permit confined space is, tell them where they are in a facility and verbally warn them as to the hazards they present. If you’re still a doubter, take a look at Federal Register, Vol. 58, No. 9, pages 4481-4484, and the answer to the fourth question in Appendix E, section (c) of CPL 2.100.

In some cases, posting may actually create another hazard. How can this be? I’ve seen lots of cases where someone has done a survey and determined at a particular point in time which spaces were permit spaces and which were not. Those that were, they posted, and those that weren’t, they didn’t.

When I’d ask what work was done in the space, they’d say something like inspection, removing materials or making mechanical adjustments. When I pressed further, they’d often point out that they might also use solvents in the space to clean or degrease parts.

What these folks failed to realize was that many confined spaces are not static environments. Things can change. In fact, they can change year to year, month to month, day to day and, in some cases, hour to hour or minute to minute.

Unfortunately, they failed to consider that job-related hazards, such as solvent vapors, could turn a nonpermit space into a permit space. If a space isn’t posted as a permit space, workers who enter might not think that any special precautions or permits are necessary.

The whole purpose for posting permit spaces is to notify people who might not otherwise recognize them as permit spaces and enter them inadvertently. Moreover, in the standard’s preamble, OSHA specifically points out that it does not ” … require the posting of any permit space whose only means of access necessitates the use of tools or keys, provided that the employees who are expected to gain entry into these spaces are trained to recognize the hazards involved. Restricting access to permit spaces in this manner protects employees effectively without the use of signs.” (Federal Register, Vol. 58, No. 9, page 4484.)

The key thing to remember here is that employees must be informed of the hazards posed by confined spaces. If you want to label your spaces, you might want to consider labeling all of them. You might also want to consider adding an admonition to check with a designated authority before entering any of these spaces.

Atmospheric Hazard Myths

Myth: The atmosphere in a confined space can change in the blink of an eye.

Fact: The laws of chemistry and physics prohibit the atmosphere from changing instantaneously. For example, the oxygen content in a space won’t be 20.8 percent one minute and 0 percent the next.

Yes, the atmosphere in a confined space can change, but it will always change at some rate. If the space is monitored continuously with an appropriately selected instrument that has been properly calibrated and set to alarm at a specified contaminant concentration, the alarm will sound when the contaminant level reaches that prescribed level, signaling the entrants that they need to evacuate.

Although it’s unlikely that confined space atmospheres will change instantaneously, they can change over time. This is why past history of a space’s atmosphere doesn’t provide any indication of its present condition. Consequently, it’s prudent to not only test confined spaces prior to entry, but also to provide continuous air monitoring when technology to provide such monitoring exists.

Myth: A confined space with an oxygen level of 19.5 percent is “safe” for entry.

Fact: A confined space with an atmosphere that contains 19.5 percent oxygen may be immediately dangerous to life or health (IDLH). The two principal ways in which an oxygen deficiency may arise in a confined space are displacement with inert gases such as argon, helium or nitrogen, and consumption by combustion or corrosion.

While a detailed discussion of why atmospheres of less than 19.5 percent oxygen are hazardous is beyond the scope of this article, additional information on this subject may be found in my article “Confined Spaces: Is 19.5 Percent Oxygen Really ‘Safe’?” (OH, June 1999.) For our purposes, suffice it to say that an oxygen level of 19.5 percent means that there is approximately 7.5 percent, or 75,000 ppm, of something else inside the space. That may not be a significant problem if that 75,000 ppm is an inert gas such as nitrogen, argon or helium, but it’s different if the contaminant is a solvent, such as n-hexane.

The ACGIH Threshold Limit Value (TLV) and IDLH value for n-hexane are 50 ppm and 1,100 ppm, respectively. So a space containing 75,000 ppm n-hexane would be 1,500 times over the TLV and 68 times over the IDLH level. Thus, even though the space contained 19.5 percent oxygen, it would clearly not be considered “safe” for entry.

Myth: A confined space with a flammable gas concentration less than 10 percent LFL is “safe” for entry.

Fact: If you read the definition for a “hazardous atmosphere” in 29 CFR 1910.146(b), you’ll see that it doesn’t say that atmospheres containing 10 percent LFL or less are “safe.” It says that those containing more than 10 percent LFL are hazardous. For example, toluene has a LFL of 1.1 percent, or 11,000 ppm. Ten percent of the LFL is 1,100 ppm. While this atmosphere may be suitable for entry from a fire and explosion perspective, it’s 20 times over toluene’s TLV of 50 ppm and more than twice its IDLH level of 500 ppm.

Myth: A confined space with an atmosphere greater that 10 percent LFL cannot be entered.

Fact: In a letter of interpretation dated Sept. 4, 1996, to Macon Jones of Blasting Cleaning Products Ltd. in Oakville, Ontario, John B. Miles Jr., then OSHA’s directorate of compliance programs, stated that “[t]he permit-required confined spaces standard (29 CFR 1910.146) does not prohibit working in a permit-required space where the atmosphere is above 10 percent of the LFL. Once the atmosphere is above 10 percent of the LFL, all of the requirements of the standard must be met.” (Go to www.osha-slc.gov/OshDoc/Interp_data/I19960904c.html .)

In other words, spaces with atmospheres greater than 10 percent LFL may be entered, but only under the auspices of a comprehensive, written confined space program that meets all of the requirements outlined in 29 CFR 1910.146(d).

Myth: A concentration of atmospheric contaminants in excess of the OSHA PEL makes a confined space a permit-required space.

Fact: First of all, no self-respecting safety and health professional should even be relying on OSHA PELs. The PELs are based on the 1968 ACGIH TLVs, which are more than 30 years old. As a practical matter, the current TLVs are a more appropriate tool to use than OSHA’s woefully outdated PELs.

Second, just because the atmosphere in a confined space is over the TLV doesn’t necessarily mean that a confined space is a permit-required space. The footnote that accompanies the definition of a hazardous atmosphere in 29 CFR 1910.146(b) states that “… atmospheric concentrations of any substance that is not capable of causing death, incapacitation, impairment or ability to self-rescue, injury or acute illness due to its health effects is not covered by this provision” [emphasis added].

The TLVs for some chemicals are established because the substance is a nuisance at the TLV concentration, not because it poses an acute health hazard. Consequently, just because a contaminant level exceeds the TLV doesn’t mean that a “hazardous atmosphere” is present. For a “hazardous atmosphere” to exist, the substance of interest must be one that poses acute health effects or that might impede an entrant’s ability to escape in an emergency. Some materials, like asbestos and arsenic, don’t meet that criteria; others, like most solvent vapors and gases such as H2S, SO2, Cl2, O3, COCl2, do.

Further guidance on this topic can be found in a letter of interpretation dated March 26, 1999, to Marc A. Viera of SAGE Environmental in Pawtucket, R.I. (http://www.osh-slc.gov/OshDoc/Interp_data/I19990326.html). In that letter, Richard Fairfax, OSHA’s director of compliance programs, wrote that “[t]he preamble to the Permit-Required Confined Space standard (Federal Register, Jan. 14, 1993, Vol. 58, No. 9, page 4474) clearly states that an atmosphere that contains a substance at a concentration exceeding a permissible exposure limit intended solely to prevent long-term adverse health effects is not considered to be a hazardous atmosphere on that basis alone. Therefore, if the atmosphere is above the PEL, then it would not automatically be classified as a “hazardous atmosphere.”

Read the rest of the story here: http://ehstoday.com/safety/confined-spaces/ehs_imp_34100?goback=.gde_2246751_member_229555616

Source: EHS Today®