Ventilating a confined space isn't just about flipping on a fan and calling it a day. There’s an art—and a bit of science—to getting it right. If you don’t, you could be putting yourself and your team at risk. Let's break down four common mistakes people make when ventilating confined spaces: short-circuiting, recirculation, inadequate CFM, and bending ductwork like it’s a contortionist’s routine.

1. Short Circuiting

We’re not talking about blowing a fuse here—this short circuit is all about airflow. Picture this: you set up your ventilation to push fresh air into a confined space, but instead of circulating throughout the area, the air takes a shortcut right out of the portal. The result? Only a fraction of the space is getting ventilated, potentially leaving atmospheric contaminants in the space or workers’ breathing zone.

To avoid this, don’t just place your ventilation gear down and hope for the best. position the intake and exhaust strategically—ideally, on opposite ends of the space. Make sure that fresh air travels through the entire space, hitting every nook and cranny, before it exits. If the space in question only has a single portal, ensure that the ductwork is long enough and configured in a way that allows for ventilation in the area that work is taking place. On a side note, longer ductwork can result in decreased overall CFM – check with your manufacturer for details.

Recirculating air might be great for your car’s A/C, but in confined spaces, it can be a fatal mistake. If the air you’re pulling out of the space ends up getting sucked back in, you’re just circulating the same contaminated air over and over again. While the space may feel like it is being ventilated, the contaminates never get diluted out since they are being reintroduced back into the space with each air change.

The fix? Make sure the intake of your ventilation system is positioned in an area that is pulling clean air into the space and ensure the exhaust air is vented far away from the intake. Keep the intake and exhaust well-separated to avoid creating this vicious cycle.

3. Inadequate Ventilation Flow Rates

CFM, or Cubic Feet per Minute, is ventilation’s way of saying “How much air am I actually moving here?” If you don’t have enough CFM, you’re not pushing out the bad air fast enough, and the space could stay hazardous longer than you’d like, or possibly, not control the hazard at all.

Before you set up, do the math. Figure out how much air you need to move based on the size of the space and the level of contaminants you’re dealing with. Too little CFM, and you’re not doing much good. There are multiple methods to calculate the CFM required for your space (I know, math…) however, there are online calculators that can assist with this if math isn’t your strong suit. The typical formula starts with determining the volume of the confined space in cubic feet and the deciding the number of air changes per hour (ACH) required by your organization. 

"While OSHA and ANSI don't recommend a specific number of air changes per hour, a general rule of thumb is around 7 ACH before beginning work. The American Conference of Governmental Industrial Hygienists (ACGIH) recommends 20 ACH when ventilating confined spaces". 

To calculate the CFM requirements, multiple the confined space volume by the air changes per hour and divide that number by 60.

Example:

CFM =  Volume of space (ft³) X Air Changes Per Hour / 60 minutes

CFM =  2500 ft³ X 20 ACH / 60 min

CFM =  50,000 / 60 min

CFM = 833 ft³/min

After you’ve figured out your minimum CFM requirements, you can determine your minimum purge time prior to entry. You can choose to manually calculate this, use an online calculator, or use a ventilation purge time chart like the one provided here. This chart is calibrated to provide a pre-entry purge time representative of 7 complete air changes.

If you're into doing math, the formula below can be used to calculate your pre-entry purge time.

Example: 

Purge Time = Volume of Space X Pre-Entry Air Changes / CFM

Purge Time =  2500 ft³  X 7 Air Changes / 833 ft³/min

Purge Time =  17,500 / 833 ft³/min

Purge Time = 21 minutes

Ever try to suck a thick milkshake through a crazy straw? That’s what too many bends in your ventilation ducts can do to your airflow. Every bend creates resistance, slowing down the air and reducing the overall effective CFM of your ventilation system.

To avoid this, keep your ducting as straight as possible. If you do need to make a turn, go for gradual curves instead of sharp bends. This keeps the air moving smoothly and ensures that you’re getting the ventilation you need where it’s needed most. As with any piece of equipment, check the manufacturer’s guidelines for specific information. While every manufacturer will have their own guidelines for their products, most manufacturers rate their products as a decrease of around 15% per 90-degree bend with a max of two 90-degree bends. Typically this information will be provided on the device itself as seen in the picture below.

Conclusion

Ventilating a confined space is more than just a box to check—it’s about creating a safe atmosphere to work and breath in, or at least controlling the hazards to a level that’s as low as reasonably practicable. By avoiding these common pitfalls, you’re not just moving air; you’re ensuring that it’s doing its job effectively. So next time you’re setting up ventilation, remember: keep the air flowing where it needs to go, and don’t let short circuits, recirculation, inadequate CFM, or ductwork disasters stand in your way. Proper ventilation is a breath of fresh air – literally…..

ONLINE REFERENCES:

ACGIH: Ventilation

OSHA 1910.146: Permit-Required Confined Spaces

ANSI Z117.1 - 2022: Safety Requirements for Entering Confined Spaces

Chris McGlynn, M.S., CSP is a Certified Safety Professional and Nationally Registered Paramedic who serves as the Director of Safety and VPP Coordinator for Roco Rescue. He currently serves as Director-at-Large on the VPPPA Region VI Board of Directors and Secretary of the American Society of Safety Professionals Region IV Board of Directors. Chris also represents ASSP on the ANSI Z117 Confined Space and Z390 Hydrogen Sulfide Training Standard Development Committees. He is also an active OSHA Special Government Employee within the Voluntary Protection Program and is currently working towards a Ph.D in Occupational Safety & Health through West Virginia University's Statler College of Engineering. 

In recognition of Chief Instructor Bobby (BK) Kauer’s assistance with several real rescues alongside Wellsville EMS & Rescue and Western New York Ambulance Corps, we are featuring Chief Kauer in our Employee Spotlight.

This past month, we received several great emails and phone calls in appreciation for the services rendered by Chief Kauer when he was conducting a rescue course for the Wellsville EMS and Rescue Squad in New York.

Chief Kauer responded to one emergency incident involving a 600+ lb. fall victim, which was featured here in ROCO RESCUE TALK™. According to Paramedic Andrew Sweezy of the Wellsville Volunteer Ambulance Corp Rescue Squad, “Without the skills learned via ROCO being rapidly implemented, patient extraction would have been severely delayed and most likely resulted in responder injuries or a much worse (or fatal) outcome for the patient who was rapidly deteriorating.” As was the responding agency, we are grateful and proud of Chief Kauer’s willingness to help with this incident – all while watching his brand-new students perform their newly learned and enhanced rescue skills.

Then came Tropical Storm Debbie. When Chief Kauer went back for his second weekend of training, the area was getting torrential rains from T.S. Debbie. Chief Kauer once again went into action with his students to perform several high-line water rescues. Wellsville Rescue Chief Chris Martelle stated, “It was great to see the students working hand-in-hand with their instructor to perform live rescues.”

He added that they had several other incidents throughout the weekend that Chief Kauer assisted with. Chief Martelle commented that Chief “BK” Kauer is not only a great instructor, but also a great friend. He added, “We are absolutely grateful for Chief Kauer. He knew we were exhausted from the multiple incidents, and he stepped in and assisted.” And perhaps best of all, Chief Martelle added, “BK has a huge heart to not only teach classes but also to help people in their darkest hour.”

Here's a little more background information on Chief Bobby Kauer. Chief Kauer (more commonly known as “B.K.”) has two highly visible roles at Roco – one in services and one in training. In services, he manages a growing portfolio of business for Roco’s Contracted Safety and Rescue Teams (CSRT) for the Northeast. In this role, he interfaces with customers to assess jobs and coordinates with his team of experienced rescuers to staff jobs all over the Northeast. In his role as Chief Instructor with Roco, B.K. teaches on a wide variety of topics including rope rescue, confined space rescue, trench rescue, and fall protection.

B.K. began working for Roco Rescue in 2004; however, his roots in technical rescue originate from his 22-year career with New York City’s Department of Corrections (see below), where he was on the Emergency Services Unit (ESU). In that role, he trained alongside NYPD’s Emergency Services Unit, and later was an ESU Instructor. He was a first responder at Ground Zero on 9/11 and performed search and recovery work for four months afterwards.

Here at Roco, we are very grateful for Chief Kauer and his many years of service. We also are very proud of his dedication to emergency responders and willingness to help others.

New York Department of Corrections (DOC) Emergency Service Unit (ESU)

Emergency Services Unit (ESU) responds to all emergencies within the Department of Corrections, both on and off Rikers Island. ESU responds to various incidents, including fire emergencies, high security inmate transport, riot control, inmate escapes, tactical security operations, cell extractions, perimeter security/response, confined space rescue, and vehicle emergencies (i.e. vehicle accidents). ESU also responds to all emergency drills, provides EMT response, and assists the Port Authority with possible air disasters or related events that may arise. Other duties include assisting the Special Operations Division with security breaches and enhanced security for Rikers Island during emergencies.

Are you struggling to navigate the complexities of confined space classifications? If so, you may find our latest white paper useful. This detailed analysis offers clear, practical guidance on determining whether a confined space requires a permit or can be managed under alternate entry or reclassification procedures, simplifying compliance for anyone managing a permit-required confined space program.

This guide will improve your understanding of how to properly apply the (c)(5) and (c)(7) procedures, ensuring the highest safety standards at your site. You’ll gain insights into avoiding common pitfalls, such as the prohibited practice of combining C5 and C7, which can prevent costly mistakes and ensure adherence to OSHA regulations. The paper also includes a C5/C7 Quick Reference Guide, designed to provide quick answers and streamline your decision-making process.

This paper explains the terms and requirements of C5 and C7 with straightforward language and real-world examples. It provides actionable steps to help you classify and manage confined spaces safely and efficiently. Equip yourself with the knowledge to make informed decisions about confined space safety.

Interested in a workshop or consultation from Roco Rescue? Contact us at 800-647-7626 or info@rocorescue.com.

Enhance your confined space safety program with expert insights and practical solutions.

Download Here!

Perhaps the most commonly confused topic in confined space entry that I hear out in the wild is the difference between the terms entry and bodily enter. And it makes sense because, at face value, these two things sound incredibly similar. However, when we dig a little deeper and put into context, we’ll find out that they have two entirely different meanings and applications. So, let’s dive in!

To set the stage, let’s do a quick overview of the three characteristics that define a confined space. OSHA says that a confined space is a space that:

• Has limited means of access and egress, and
• Is not designed for continuous human occupancy, and
• Is large enough to bodily enter and perform work.

Remember that the space must contain all three characteristics for it to be considered a confined space. Notice the 3rd bullet point – large enough to bodily enter and perform work. We must be able to physically fit our body into the space and perform the assigned task. Now, the use of the term bodily enter stops with the definition.

Next, let’s look at what defines an entry. OSHA says an entry has occurred when any part of the entrant’s body breaks the plane of an opening into a confined space. Notice that making entry into a confined space does not necessarily mean entering with the whole body. In fact, only reaching your arm into the opening of the confined space constitutes an entry.

"So, here’s the difference. The ability to bodily enter is one of the three characteristics that define a confined space, whereas the term entry is the action of breaking the plane with any part of the body – not necessarily the whole body."

At this point, you may be thinking this is nothing more than semantics; however, this is an incredibly important differentiation.

When we understand that making entry into a confined space does not have to involve entering with our entire body, we may realize that workers in our area may have been making a lot more confined space entries than we realized. I’ve heard on numerous occasions and even seen it firsthand, where a worker sticks their arm in to turn valves or pokes their head in for a quick peek at something without going through the permit-required confined space entry procedure. After all, it’ll only take a second!

The reason this is important, and why it’s more than just semantics, is that even though a worker may be only just sticking their arm or head into a space, they could still be exposed to the hazards inside of that space. In some cases, that could have some serious consequences! For example, there may be exposed and activated rotating equipment inside of the space; so, sticking your arm or hand in may result in you being less handy around the worksite than you used to be! Alternatively, atmospheric hazards don’t just magically stop becoming hazardous right at the plane of the opening. The immediate area around the opening of the space could likely contain hazardous atmospheres as well. Sticking your head in for a quick look could be a fatal mistake.

"The time you save isn’t worth your life."

Understanding the difference between the two terms is critical for ensuring the safety of workers in and around confined spaces. The difference between the two carries significant weight, not only in definition but also in practical application. Knowing that crossing the opening of a confined space, even with just a limb, constitutes an entry and potential exposure to serious safety and health hazards is a basic fundamental concept that all workers should be well informed. So, the next time you think – I’ll just reach in and turn that valve or take a quick look – slow down and think! The time you save isn’t worth your life.

ONLINE REFERENCES:

OSHA 1910.146 PRCS

Chris McGlynn, M.S., CSP is a Certified Safety Professional and Nationally Registered Paramedic who serves as the Director of Safety and VPP Coordinator for Roco Rescue. He currently serves as Director-at-Large on the VPPPA Region VI Board of Directors and is past President of the American Society of Safety Professionals Greater Baton Rouge Chapter. Chris also represents ASSP on the ANSI Z117 Confined Space and Z390 Hydrogen Sulfide Training Standard Development Committees. He is also an active OSHA Special Government Employee within the Voluntary Protection Program.

Medical calls make up the majority of contacts with the public for emergency responders. Technical rescue calls make up a much smaller segment of emergency response. While the response numbers are at opposite ends of the response spectrum, they are invariably tied together.

Oftentimes, technical rescue responses originate after medical responders determine that their patient is in an untenable position. Other times, we just need more muscle than the people we responded with can muster. That is where one Western New York Ambulance Service melded EMS response with rope rescue ingenuity to provide a positive outcome for a 600-lb. bariatric patient.

Wellsville Volunteer Ambulance Corps takes the concept of self-sufficiency seriously. Located in rural western New York, 15 miles north of the Pennsylvania border, they are remote, but they know how to get things done.

In early August 2024, Wellsville was hosting Roco Rescue and Roco Chief Instructor Bob Kauer for four days of Rope Rescue and Confined Space training. At 4PM on the second day of class, EMS was dispatched for a man down in a residence. That call triggered a multi-faceted response as responders quickly learned that a 600-lb. man had been down on the floor since 9:30 the previous night. The race was on to get the patient in respiratory distress to definitive care.

While EMS responders started patient care, students from the Roco class quickly broke down rescue gear and loaded on to response vehicles. This included Roco Instructor Kauer who was happy to lend his experience and training to the response.

The first obstacle was getting the patient off the floor. He was unable to assist rescuers who were now faced with lifting the 600-lb. man. A stokes basket was brought into the living room where the man was located. A group of ten rescuers was able to slide four sheets under the patient, and a couple of additional pieces of webbing were positioned for better handling of the patient. The man was then lifted into the basket stretcher.

While responders were moving the man into the basket, rescuers were working to build a system to move the patient to the waiting ambulance. Chainsaws were fired up and the front door was rapidly converted to a garage door to make room. A support beam for the porch had to be removed, requiring rescuers to place spot shores under the porch to provide for patient and rescuer safety during the move. Ramps were built using plywood and 4” x 4” lumber to remove the stairs from the equation.

Meanwhile, outside the house, rescuers, including Chief Kauer, established an elevated anchor on a large tree. A CMC Clutch by Harken became the progress capture device in a 5:1 horizontal mechanical advantage system. Quickly extended into the residence, the system was attached to the top of the stokes basket and tensioned. The haul team began to move the patient in the stokes basket across the floor and the emergency ramp system they had constructed, which allowed the victim to slide straight onto the gurney.

The patient was loaded into the ambulance and delivered to the hospital for definitive care in less than an hour, which was excellent.

Roco extends our congratulations to Wellsville (NY) Volunteer Ambulance Corps for a well planned and executed rescue. Good job!!