Type Y & Z NFPA 496 Enclosure Pressurization Unit Capacities

Unit Capacities

Best Purging Systems Corporation offers a wide array of enclosure pressurization units to satisfy applications for enclosures ranging from volumes up to two(2) cubic feet to a maximum volume of up to two hundred and fifty (250) cubic feet!

As shown in the image to the right, the size differences of the units is slight, but the enclosure supply regulator and tube fittings of each unit range from 1/4″ to 3/8″ to 1/2″ to provide the significant degree of increased capacity required to hold a safe pressure on increasingly larger protected enclosures.

Years of practical experience has proven that as enclosure volumes increase, the amount of leakage around doors, cover plates, access panels and even supposedly sealed conduit fittings typically increases at an exponential rate.

However, careful design and proper maintenance of a protected enclosure can minimize the amount of air consumption required to hold a safe protected enclosure pressure.

For more information regarding our unit capacities and for technical assistance regarding protected enclosure design factors that dramatically affect air consumption, please call us and ask to speak with a Technical Advisor. We’re always glad to assist you in any way possible to achieve the most effective and safe use of our products!

The following chart provides each Unit’s total capacity, based upon the total cubic footage of enclosure volume, not excluding any volumes consumed by internal equipment.

When pressurizing multiple enclosures, the cubic footage of each enclosure must be added together to develop the total volume.

To calculate enclosure volume in cubic feet, multiply the height by the width by the depth.

Model Number

Area Classification



Class I

Up to 2 Cubic Feet


Class II

Up to 10 Cubic Feet


Class II

Up to 50 Cubic Feet


Class II

Up to 250 Cubic Feet