Oxygen Displacement Calculations for Confined Space Rescue

In a previous post, I discussed atmospheric hazards related to oxygen deficient and enriched environments. One of the ways that an atmosphere can become oxygen deficient is from another gas being introduced into the area and pushing all the oxygen out. We refer to this process as oxygen displacement. But just how much of that other gas is present? That is the answer we are going to answer today.

Let’s do the math

In order for our oxygen concentration to decrease 1% (I.E., from 20.8% to 19.8%), there needs to be five times that amount, or 5% of another gas pushing it out. The reason for that is because oxygen is only 1/5 of the normal atmosphere. Let’s remember that we can also express percent of atmosphere in terms of parts per million (PPM), with 1% equaling 10,000 PPM.


Step 1 – Subtract your current oxygen percentage from 20.8 to determine how much it decreased.

Step 2 – Multiply that number by 10,000 to convert it to PPM.

Step 3 – Multiply that number by 5 to account for the fact that oxygen is only 1/5 of normal atmosphere.

Practical application

Observe the readings on the detector and calculate how much of another gas is present in the confined space.

Step 1 – 20.8% – 19.1% = 1.7%

Step 2 – 1.7% x 10,000 = 17,000 PPM

Step 3 – 17,000 PPM x 5 = 85,000 PPM

That is A LOT of another gas! It could easily be well above the immediately dangerous to life and health (IDLH) level for that gas. If your detector does not have a sensor capable of detecting the displacing gas, you may have no indication that it is present other than your oxygen percentage decreasing. The moral of the story is that any drop in your oxygen percentage may indicate something bad is present!

Bill Elder
Owner / Lead Instructor
Elder Technical Rescue Services, LLC

Lessons Learned from a Confined Space Rescue LODD

Confined space fatalities are often associated with atmospheric hazards and the “would-be rescuer syndrome.” In this incident which occurred ten years ago, a public works employee and the firefighter who first attempted to rescue him were killed. This post is a summary of the NIOSH LODD Report.

The Incident

On September 6, 2010, a firefighter was killed when he entered a confined space to rescue a utility worker. The incident occurred in a sewer manhole right behind the firehouse. Several firefighters had been on-location while public works employees worked on a sewer problem.

After one of the public works employees entered the space and immediately became unconscious, one of the firefighters who was on-location entered the space to retrieve him prior to any atmospheric monitoring being performed. After making it halfway down the ladder, the firefighter also became unconscious and fell the rest of the way into the confined space. At that point, atmospheric monitoring was conducted, and a technical rescue team was requested to assist. Witnesses stated the oxygen readings in the space were between 11 – 14%. Both the public works employee and the firefighter died from asphyxia and exposure to sewer gases.

Source: NIOSH LODD Report

Lessons Learned

The most important lesson learned from this incident is that first responders must be trained to a minimum of the awareness level in confined space rescue. It is critically important that first responders understand what confined spaces are, recognize the hazards that exist in them, and know how to request additional resources to the scene of these incidents.

Other lessons learned include ensuring your agency has a standard operating guideline (SOG) for responding to confined space rescue incidents. Even if your agency is only going to provide an awareness level response, developing a response SOG will still help ensure your organization’s members know what actions to take (and not take) at these types of emergencies. If you are going to respond at the operations or technician levels, SOGs are still very important because they define your organization’s expectations on how to safely operate at these incidents.

Furthermore, SOGs and real-world responses to these types of emergencies must include the use of the incident management system and assigning a safety officer that is knowledgeable in confined space rescue. Another very important position to assign at confined space rescue incidents is the “Attendant.” This individual prevents unauthorized entry into the space. Nobody should enter the confined space unless authorized by the rescue supervisor and/or incident commander!

Confined Space Rescue Training

Elder Technical Rescue Services, LLC offers Confined Space Rescue Awareness (3 hours), Confined Space Rescue Operations (16 hours), and Confined Space Rescue Refresher (8 hours) training programs. Our operations level program is now available in a blended learning format, and can be utilized by individual students and groups. Contact us to setup a class for your agency.

Bill Elder
Owner / Lead Instructor
Elder Technical Rescue Services, LLC

New Course – Advanced Rescue Techniques!

I’m happy to announce a new course has been added to our training catalog.  Advanced Rescue Techniques (16 hours) is designed to expand upon the students’ existing operations level skills with additional tactics, techniques, and procedures. The program can be customized to meet the needs of the students but will always include a review of relevant background information, standards and regulations, patient assessment and packaging, and advanced practical scenarios.

Agencies scheduling this course will select the specific disciplines and techniques they wish to focus on in the program. Techniques from the rope, confined space, tower, and water rescue disciplines can be selected. Training officers will be given a list of all the advanced skills available with reference to the current NFPA 1006 standard, and we will work with them to create a custom course of instruction.


If you are interested in setting up a custom Advanced Rescue Techniques course for your agency, let me know!  I am very excited to offer truly customizable rescue training programs based on the needs of your agency.

Bill Elder
Owner / Lead Instructor
Elder Technical Rescue Services, LLC

GORUCK Rigging Bag Overview

We recently switched up our rigging bags to two GORUCK GR0/GR1 rucks, and we wanted to share our set up with all of you.  If you are not familiar with GORUCK, please check out their web site.  The long and short of their company is that they were founded by a former Green Beret and they manufacture some fantastic gear in addition to hosting rucking events that will push you and your team members beyond your physical and mental comfort zones.


I have been wearing my GR0 bag (pictured above, right) for several years and after some experimenting, decided to acquire a newer GR1 bag and make them rigging bags for ETRS technical rescue courses.

Here are the contents of each bag:

5 – Carabiners
3 – Tri-Links
1 – Swivel
1 – Rigging Plate
1 – Double Pulley
2 – Single Pulley
2 – Sets of Prussiks
2 – Descent Control Devices
1 – ASAP
1 – Work Positioning Strap
1 – Anchor Strap
1 – Set of Fours
2 – Lengths of Webbing (15′ and 20′)
1 – SMC Flex (Edge Pro)
1 – 3″ Fire Hose (Edge Pro)


Each bag has some slight variations in specific makes and models of the equipment.  This allows us to introduce our students to different types of equipment on the market and discuss topics such as NFPA 1983 ratings.  For example, one bag has steel G-Rated carabiners, while the other has aluminum T-Rated carabiners.  We also have a variety of descent control devices (Petzl ID, Petzl Maestro, ISC D5), work positioning straps (Petzl Grillon, Kong Trimmer) and sets of fours (Petzl JAG, Aztek Kit).

The bags remain remarkably light and ergonomical and allow students in our small group classes to split up and accomplish their rigging objectives without breaking their backs.

Check out our Rope Rescue Operations – Blended Learning program or private rope rescue training sessions if you want to do some training and check out our bags in person.

Bill Elder
Owner / Lead Instructor
Elder Technical Rescue Services, LLC

Confined Space Rescue Operations (Blended Learning) Coming Soon!

We are excited to announce that we are currently reviewing the first draft of our upcoming Confined Space Rescue Operations (Blended Learning) program.  This course will allow students to complete the cognitive portion of Confined Space Rescue Operations class online, at their own pace.  Upon completion of the online component, the student will participate in a full day of hands-on practical skills training in order to receive the Confined Space Rescue Operations (16 hours) Certificate of Continuing Education.


The pre-requisites for this course will be previous Hazardous Materials Operations Level and Rope Rescue Operations Level training.  For those totally new to the technical rescue world, this course will be available as a bundle with our existing Rope Rescue Operations (Blended Learning) course.

We still have a lot of work to do on this program, but we wanted to let you know that it is on the way.  We are dedicated to providing high-quality and flexible training options that produce competent rescuers.

Bill Elder
Owner / Lead Instructor
Elder Technical Rescue Services, LLC