Air Changes Per Hour, Infection Control and Dust Containment

This post continues our blog's examination of the exciting world of dust, why dust can be dangerous and the 'art' of containment. Again, the goal of this blog is to provide the very basics, the foundation, of infection and dust control.

I have written over the past two months about:

1. How dust becomes infected and what is in dust.
2. Dust containment and the HEPA-filtration standard as to the prevention of hospital acquired infections.
3. The relationship air-flow and air-pressure have to filtration and containment.

There is another important component to air-flow, air-pressure, filtration and containment related to infection control practices that we have not discussed. The actual calculation of air-flow often as a cited criteria for effective containment is known as Air changes per hour or ACH. ACH is simply the measure of air volume that can be added/removed from a space in a given hour. One air change results when all air has been replaced. It is a complete recycling of the air.

It might seem complex but the calculation is simply: Air Changes Per Hour = Volume of Air Flow in cubic ft. per minute (60) / Cubic feet of the area. In practical terms, a negative air machine with a cfm of 500 (pulling 500 cubic ft. per minute) pulling from a 2,000 cubic foot area is 500 cubic feet x 60 minutes / 2000 cubic feet = 15 Air Changes Per Hour or ACH. 

General guidelines are that spaces with immunocompromised patients have 15 ACH or more. If there are not immunocompromised patients then many facilities accept 12 ACH. Operating and delivery rooms usually have recirculating air systems that provide 25 ACH.

It is critical that you have a fan unit that can pull the necessary air-flow to meet those guidelines in healthcare facilities. If you are shopping for specific HEPA-filtration devices, it is imperative to have an industrial grade, true HEPA 99.97% that can move 300-800 CFM (depending on the volume of space being filtered of course). It may even take more cfm to achieve the correct ACH. 

This is why our sealed, tested and certified (HEPA 99.99%) air filtration units at HEPACART™ are variable speed and can adjust to the CFM you need for properly pulling the correct amount of air, filtering infected dust and providing you with the required ACH for that space. We also provide larger fans rated up to 1500 cfm for larger areas should that need arise.

At HEPACART™, we believe there is an art to the containment. Our next blog will focus on the elements involved in that art and how they all work together to protect people and increase productivity. Let us know if we can help with your next containment project.