VENTILATION

In general, it is a good idea, and in some cases, it’s required under OSHA regulations to ventilate a confined space before entry and to maintain forced ventilation while the space is occupied. Forced ventilation is required to remove air contaminants, provide oxygen, and to keep the air as clean as possible.

Information on individual confined space ventilation products can be found on their pages by following the links. For more information on atmospheric hazards, forced air ventilation, gas monitoring, or other worksite safety and equipment questions, consult PK Safety’s website and blog or talk to one of our safety experts. Also check out other confined space gear including our confined space kits, confined space signs and confined space retrieval systems.

How do I ventilate a confined space?

Ventilating a confined space involves removing atmospheric hazards by introducing fresh air into the space, removing stale air or contaminants, or a combination of the two. There are two options for ventilating a confined space. Forced-air ventilation uses fresh air, forced in by a fan, to ventilate a confined space by way of forcing in fresh air that displaces contaminants and dilutes the stale or contaminated air already in the space. Exhaust ventilation uses an exhaust system to remove contaminants at the source. Ventilation blowers or exhaust systems are usually attached to a space by way of a duct to help direct the airflow.

How do I calculate the ventilation rate for a confined space?

The size and shape of a confined space, as well as the work being done there, will affect the ventilation requirements. Before you calculate the minimum required ventilation rate, you need to know the size of the space in cubic feet and the air changes (number of times the air must be replaced based on legal limits as well as company policy) per hour. Multiplying these two numbers together gets you the total cubic feet per minute (CFM) requirement. This result is the minimum rate of ventilation required for your confined space. An irregularly shaped space will likely require a greater CFM blower to properly ventilate. Turns, corners, bulky equipment, and even the ducts themselves can further restrict airflow, which may impact CFM calculations. You may need to also take into account available power sources, how stable those sources are, and other equipment that will be drawing power from those sources.

Why is ventilation important when welding in a confined space?

Welding in a confined space creates very dangerous conditions that can include a lack of oxygen, fires and heat, and toxic gasses to be inhaled. Luckily, ventilation can help mitigate some of these risks. OSHA lays out very specific requirements for welding in confined spaces because of this. If an area can’t be properly ventilated, welders need to use airline respirators and be in constant communication with outside coworkers (which is also a good idea even if you aren’t welding). Have pre-planned rescue procedures whenever you’re doing any work in confined spaces, and make sure that the air is tested. Also, ensure that there’s a way to shut off dangerous equipment from inside the workspace if possible and that the exits aren’t blocked.

Should you ventilate before entering a confined space?

You absolutely should! Ventilating a confined space helps control fumes, dust, vapors, mists, and other contaminants and atmospheric hazards. It helps to both bring in fresh air and keep dangerous materials to a low enough exposure limit to make the environment safe enough for humans. Such precautions help provide protection in case more hazards are released, remove contaminants that are already in the space, and keep things cool and comfortable.

However, you should also continuously ventilate, monitor, and test the space while work is being done. Conditions can change suddenly, and in confined spaces it’s especially crucial to respond to hazards in a timely manner to avoid anyone getting trapped or seriously hurt or sick. Keep ventilating a space as long as there are workers inside.