Confined spaces may be encountered in virtually any occupation; therefore, their recognition is the first step in preventing fatalities. Since deaths in confined spaces often occur because the atmosphere is oxygen-deficient, toxic or combustible, confined spaces that contain or have the potential to contain a serious, atmospheric hazard should be classified as Permit-required confined spaces and should be tested prior to entry and continually monitored.
Before entering any confined space and tackling any application, you must ask yourself several questions:
- Where will the blower be used?
- What is the size of the confined space?
- Is the confined space hazardous or nonhazardous?
- How much CFM from the blower is needed?
- How many times should the air in a confined space be circulated per hour?
The majority of confined space ventilation issues, and even deaths, can be prevented with education and the use of proper equipment.
Picking the Best Fan or Blower for the Job
When selecting a fan or blower, all ventilators have two characteristics:
- Air pressure– Force of air volume is measured by inch of water gauge (WG)
- Airflow– Air volume delivered and measured by cubic feet per minute (CFM)
Axial Blowers
Axial blowers create high airflow, but the blade design develops lower pressure. When used with ducting, the ventilation duct creates air movement resistance, therefore, making the axial fan inefficient at longer distances, especially with multiple bends in the ducting. Axial fans are designed with several large paddle blades that develop a large volume of airflow (CFM).
When to use Axial Blowers
They are lightweight, low cost, and best when working in smaller confined spaces and short distances with minimal ducting (preferably 15 to 25 ft. of flexible ducting).
NOTE: We also offer an Air Bag Blower, which is a metal axial blower system with ducting built into a heavy-duty polyester bag for an all-in-one unit for ease of operation and portability.
Centrifugal Blowers
Centrifugal blowers use a “squirrel cage” designed with numerous forward-curved blades on a circular wheel. The blades create significant volume (CFM) and very high air pressure (WG).
When to use Centrifugal Blowers
They are typically heavier and cost more than axial fans due to the motor required to run the blades efficiently. These blowers are used to move air a long distance, using long or multiple lengths of duct. A big advantage these blowers have over other blower types is that the air does not cross over the motor minimizing the chance of contaminating the motor.
In-line Axial Blowers
In-line Axial Blowers are used by themselves or with an additional fan/blower as a velocity accelerator for long duct distances over the 15-to-25-foot standard duct length.
When to use
When ventilating at a long distance, simply add an in-line fan to the ducting to increase or maintain airflow. In-line fans can be used with axial or centrifugal blowers to extend longer ventilation distances.
Venturi Blowers
Venturi Blowers operate with a pneumatic air hose without moving parts or blades, minimizing maintenance. Tremendous CFM is created by using a hollow hub that creates a vortex, spinning air similar to a jet engine.
When to use
With no mechanical blade, Venturi blowers are not specifically designed to force air through flexible ducting. You must have high-pressure compressed air to power these blowers. They are primarily used as a suction or push device on a tank and can be used in conjunction with an axial or centrifugal fan to remove gases from a tank rapidly. Venturi bases are designed to fit American Petroleum Institute (API) standard tanks.
Pneumatic Jet Fans
Pneumatic Jet Fans operate with a pneumatic air hose to ventilate tanks or other large areas.
When to use
This fan is designed to push air in or remove air from tanks or other large areas to rapidly remove gases. The jet fan bases are designed to fit American Petroleum Institute (API) standard tanks.
Allegro Confined Space Blower Selector Tool
We understand choosing the correct blower for your confined space site could be confusing and burdensome, and that’s why we’ve developed our Blower Selector Tool making the process as painless as possible! It’s available on our website or as a standalone app for your mobile device. So try our selector today and select the perfect Allegro blower that meets all of your confined space needs!
Allegro also offers a wide variety of blower accessories, such as our patented 8″ and 12″ Manhole Ventilation Passthrus (MVPs), Duct-to-Duct connectors, Ducting Reducers, Ducting Storage Bags, Filter Boxes, and more!
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You can reach us through our website to learn more about our high-quality Blowers and/or Fans or find sales representatives and sales managers in your area.