By: Expert No. 353399, ASP, CHMM, CET, CHCM, CHST, B.Sc. 

A breaking news story conveys tragic results of yet another confined space fatality incident.

With increases in industrial and construction activity, entry into confined space has become a more frequent workplace task.

Fatality statistics indicates that over 60 percent of rescues in confined space result in a workplace fatality. As most of these cases are fully preventable, they frequently involve local emergency responders, assisting injured or trapped workers.

Early in 2017, a volunteer firefighter and two deputies were taken to the hospital for observation after three pipeline workers died in a sewer confined space, while employed by a local excavation contractor in Key Largo.1

Federal and state based OSHA programs have issued a new confined space standard for construction, codified as CFR §1926.1201. Rescuers responding to confined space incidents, or those involved in onsite rescue, must be assessed for skills and applicability.

Employers must determine if rescuers (or their in-house team) are capable of and have the required equipment to meet the rigors and technical demands of site-specific rescue.

As an example, confined spaces situated in high-angle or subterranean locations often have unique and exotic hazards.

Rescuers must be capable of performing duties in these zones, deploying complex rescue systems based upon practical knowledge of the hazards at hand. They must be able to set up specialty rescue equipment to protect entry teams during rescue, or emergency medical response in extreme environments.

In order to develop a professional rescuer, mandatory training, material resources, and practical skills must be gained at the operations level: fire department or industrial rescue squad.

Confined space rescue technology is not auto-intuitive, and skills are perishable.

To retain skillset responders should have frequent drills and retraining as required.

A common misunderstanding suggests that all responders arrive, ready-to-roll with confined space rescue proficiency. It’s unreasonable to expect that all responders (rescuers) will be trained and equipped to the same standard.

New and improved rescue protocols are being developed every day. As Michael Smith, a professional firefighter reminds us, “Emergency scenes are dangerous and potentially lethal! Why? Because of the lack of control. There is no other job that allows or requires its employees to work in an uncontrolled environment.”

Therefore, to lessen lethality or risk, controls must be put in place for confined space rescue and training.

Serving to alert responders in advance, testing air during emergency medical dispatch, EMT’s can detect carbon monoxide levels in a structure or residence if a CO detector is deployed.

Air Testing during Size-up

To conduct an atmospheric test for hazardous gas in route to the confined space, a size-up or sampling of air is performed, as illustrated in Figure 1.1.

En route to an underground bunker type confined space, responders are able to know in advance of arrival, if safe air exists before removing or opening the entry portal.

In this illustration of a confined space, and due to immediate proximity to a gas fired power plant, entry procedures are being conducted per permit required confined space standards (PRCS), including advanced perimeter air testing for presence of flammable vapors or low oxygen levels.

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1 David Goodhue,

Fatal Error

During a confined space incident in Middletown Ohio2, May 7, 2010, public safety officers responding to an emergency dispatch, found a 32 year old city utility worker lying motionless at the bottom of a confined space.

Upon arrival, assumptions were made regarding the cause of the 30 foot fall, as attempts to arouse the victim were unsuccessful.

When the rescuers entered the space, they too were overwhelmed by oxygen deprivation, resulting in both responders sustaining serious injury. Arriving firefighters and medevac took the victims to a critical care unit in Middletown.

The record indicated that the responders entered the confined space without breathing apparatus (BA), or gas testing equipment.

Atmospheric Anomaly

Upon completion of the post incident investigation of the confined space, it was discovered that the utility worker also failed to test the air at the entry portal. Upon his arrival, he removed the manhole cover and stood gazing into the 30 foot deep hole.

Within seconds, a jet of oxygen-depleted air impacted him, rendering him unconscious as he fell head-first into the manhole.

It was confirmed by a fire department investigator that breathing air in the space was incapable of supporting life (IDLH), less than mandatory (19.5% min.) level per Federal OSHA regulation. 3

Dangerous Assumption

Upon arrival to the scene emergency responders assumed a slip and fall accident, supposing the victim had simply fallen into the space. As a result of failing to identify toxic air, they proceeded to enter without an air test or customary respiratory protection (BA) equipment.

Completely unaware of the hidden, and dangerous (IDLH) conditions inside, they descended into an untested vertical manhole, passing-out and sustaining serious injury. As result of failing to follow established OSHA confined space regulations, multiple injuries and fatality occurred.

Federal safety administration and fire department protocol require entrants and rescuers to conduct pre entry air testing of confined spaces, even during emergency rescue. Manhole entries into live septic sewers or lift stations are inherently dangerous due to potentials for toxic gas and low-oxygen.

In the decomposition of bio-matter, oxygen displacement occurs naturally, resulting in accumulation of potentially toxic gas.

John Rekus, a consulting industrial hygienist, explains the process of decomposition stating, “Fermentation is an enzymatically controlled chemical reaction in which microorganisms digest organic matter, producing nitrogen that displaces ambient oxygen.”

Oxygen Deficiency Frequency

Historically, asphyxiation accounts for the majority of documented confined spaces fatalities. In a two-year study conducted by the National Institute of Occupational Safety and Health (NIOSH), they determined that low oxygen levels were the primary cause in multiple confined space fatality cases (1984 to 1986). The NIOSH study indicated, “Out of 188 deaths, 146 were from oxygen deficiency.”

Testing air at the exterior of a confined space entry portal may be a major first step to protect our emergency responders and rescue teams.

In proactive responder based safety training, firefighters and rescuers should modify instructional curricula, to include preemptive air testing, conducted during size-up.

A common believe that confined space atmospheric hazards exist only within the closed space or portal, has resulted in injury and fatality to emergency responders.

Many rescuers are caught-off-guard and fail to conduct a proper pre entry evaluation of atmospheric conditions at the exterior (approach) to a confined space, and/or before removing the entry cover. Even when air has been determined to be safe, responders must always remain alert to the possibility of atmospheric jetting of toxic, or bad air emanating from a recently opened portal (manhole) cover.

Although rare, the 2010 Middletown Ohio case offers sufficient warning to merit major changes in department safety protocols. As noted in recent recommendations by the U.S. Chemical Safety and Hazard Investigation Board (CSB) to the ANSI/ASSE Z117.1 standard accreditation committee.

3 CFR, 1910.146(c)(5)(ii)(C)(1)


U.S. Chemical Safety and Hazard Investigation Board Recommendations

On March 1, 2017, the U.S. Chemical Safety and Hazard Investigation Board (CSB) issued a recommendation to the American Society of Safety Engineers (ASSE) pursuant to the CSB investigation of contractor asphyxiation deaths that occurred in confined spaces at Valero refinery in 2005; CSB recommends that Safety Requirements for Confined Spaces be revised to emphasize that:

  • An oxygen-deficient atmosphere rapidly overcomes the victim
  • There is no warning before being overcome
  • An oxygen-deficient atmosphere might exist outside a confined space opening
  • Rescuers must strictly follow safe rescue proceduresAs part of the CSB’s investigation into the Valero incident, the existing standards, guidelines and practices, they concluded that, “it did not adequately address three critical elements with respect to inert gas purged confined spaces:
  • Hazardous (oxygen-depleted) atmospheres may be present outside the confined space, near openings.
  • Acute oxygen deprivation rapidly overwhelms the victim without warning; and
  • Unprotected entry into an oxygen-depleted atmosphere for any length of time, no matter how brief,can be deadly. 

    ANSI/ASSE Z117.1 Safety Requirements for Entering Confined Spaces

    In the forward (2016) of the edition to the standard, ANSI/ASSE notes that in 2009, “Oxygen deficiency was the leading atmospheric hazard that resulted in fatalities inside confined spaces.”

    Perimeter Air Testing of Confined Space (Concentric Circular Pattern)

    As can be seen from Figure 1.2 below, an entry portal exuding toxic air at the permit space (exterior). Air testing should be performed in a concentric circular manner to detect the presence of toxic or flammable gas vapor (off-gassing); this would also include low oxygen jetting from the portal.


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Should toxic, flammable, or low oxygen levels be found emanating from a confined space, testing for their presence during size-up and before removing the cover is highly advised. If the manhole or entry portal (configuration) is sealed or tightly closed, carefully “crack” the entry cover, and insert the sampling probe into the space, in order to obtain an accurate atmospheric read out.

Note: Prior to initiating air testing at the exterior, it is recommended that wind velocity and direction are determined first, in order to obtain accurate test results from the detection instrument.

Perimeter Air Testing Steps:

Air testing should be conducted at the exterior of the confined space, in route to the entry portal to identify toxic vapor (off-gassing) or oxygen-deficient atmospheres.

Step 1. Obtain a fully charged and calibrated direct read instrument, turn the instrument on, up-range and away from the confined space, then bump test the unit to confirm readings; then

Step 2. Determine wind direction and velocity, and confirm the location of the confined space entry portal.

Step 3. While heading down-range to the confined space, begin testing the air, probing in a circular array (see figure 1.1), to detect possible off-gassing of toxic, flammable vapor, or low oxygen levels; then

Step 4. Continue air test (downwind) from the portal (toxic source), and continue probing in a circular pattern, continuously referencing the instrument readout, and wind direction.

Continue air testing as you travel down- range towards the entry portal; or until you have determined that acceptable conditions are present, within close proximity to the confined space; STOP

Danger SymbolDanger: Entry Portal: Do not open entry portal

Should high levels of flammable or toxic gas be detected at the cover, evacuate persons from the area. Deploy protective measures: PPE, ventilation strategy, and fire control. Use the buddy system, informing your team, and always follow OSHA, Hazmat, and your department safety regulations.

Danger SymbolDanger :Cover Removal: Do not open the cover or hatch

Step 5. Before removing the entry cover (hatch), test the air at any available opening. If the cover is sealed or tightly closed you will need to create an opening (crack open slightly), in order to insert the test probe, and obtain a sample or reading.

Danger SymbolDanger: On vertical confined spaces, remain alert to the possibility of a jet of rising low-air emanating from the open portal. Although uncommon, this has been documented in multiple fatality cases. Should a high level of flammable/explosive/toxic vapors be detected at the entry cover (methane gas, hydrogen sulfide, carbon monoxide), deploy measures to reduce hazardous air to acceptable levels as specified in OSHA and ANSI standards; to provide safe entry conditions, test first then ventilate prior to entry.

Once you have completed your safe approach size-up and prior to physical entry into the confined space resolved any issues for safe removal of the cover, then interior air testing is the next task. OSHA requires acceptable entry conditions be determined before and during entry into confined space.

Danger SymbolDanger: Finalize air testing inside space, sampling top quadrant, middle, finally the bottom sector.

Step 6. Take your time testing air, vapor drawn into a length of flex tubing may take indeterminable amount of time to reach, and be detected by the sensors. Caveat: time contingent upon instrument pump speed, settings, length and diameter of the tubing, and efficiency of the instrument. Be patient, you only get one shot to do it right! When testing air inside at a confined space, there is no room for error!

Remote Air Sampling:

Danger SymbolDanger: Never enter a confined space to conduct air testing, use a remote probe or sample tube, until acceptable atmospheric conditions have been assured. In addition to having a gas monitor, we recommend SCBA or other supplied breathing air donned prior to entering confined space for rescue or retrieval.

Safe Air Testing of Confined Space:

Air testing of a vertical confined space should proceed from top to bottom, performed in quadrants by sampling air at the top, midway, three quarters, and ultimately the bottom sector.

Sampling must be performed methodically, in a deliberate, cautious, and determined manner to locate any and all pockets or sources of hazardous air. The longer the sample tube, the more time it will take to draw in air from the space, and to cross the sensors of the instrument.

Air sampling conducted in a reckless or hasty manner may produce spurious results endangering the health and safety of the entry team, potentially resulting in serious injury or fatality.

Focusing on the digital readout, the responder (monitoring tech) should patiently read each and every readout, per quadrant, accurately logging-in each readout to the confined space entry permit or sampling log.

Non-Absorbent Flexible Tubing Safety and Reliability:

Remote sampling with a fixed probe or length of flexible tubing connected to the sampling instrument is performed in route to and before entering a confined space. Most detection instrument manufacturers recommend using non-absorbing types of tubing for gas detection, common types: Tygon®, Teflon®, or metallic extendible probes.

There is good reason to ensure that non-absorbent tubing is available and used during air sampling, (Tyvek, Tygon, etc.).

It has been documented that some varieties of vinyl flex tubing have been known to produce dangerous and unreliable results. Instruments can register a false negative using vinyl tubing which may absorb solvent vapor directly into the wall of the tubing.

Dangerous and erroneous read-outs have shown a zero LEL at the instrument when in fact high LEL levels existed in the hole. This has been known to occur in confined spaces where flammable solvents and paints are being used.

Be very careful in selecting flexible tubing for sampling with gas detectors. Remember, never substitute a lesser quality alternative for the manufacturer’s recommended tubing for use with air testing instruments.

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1. Hughes, D., “Three Dead While Working in a Trench in Key Largo Monday Morning, (1/16/2017),

2. CFR §1926.1201, Confined Space Standard for Construction, CCR, §1950, Confined Space, California Construction Safety Orders, and

3. Baker J., and Morse J., May 7, 2010 (, “City worker killed, three firefighters hospitalized in Middletown,”
and Justice, overcome-by-fumes_201005113564.html

4. Smith, M. Firehouse, February, 28, 2002, “Two Words, Routine and Size-Up,” online article in,

5. Rekus, J, 1994, Complete Confined Spaces Handbook, pgs. 28, 29.

6. National Institute for Occupational Safety and Health (NIOSH), January 1994, “Worker Deaths in Confined Spaces”, Summary of NIOSH Surveillance & Investigative Findings.

7. SAFETRAN, LLC Confined Space Safety Training, (Level 1), Air Testing Protocol, Training for Industry, February 17, 2006

8. O’Connell, D, April 2, 2007, Confined Space Case Files, Industrial Safety and Hygiene News (ISHN), online

9. Teflon® a registered trademark of E.I. Du Pont De Nemours and Company, is high-performance gas handling tubing for industrial, laboratory and medical applications.

10. Tygon® is a registered trademark of Saint-Gobain Corporation, is high-performance gas handling tubing for industrial, laboratory and medical applications.