ULPA vs. HEPA filters


American Cleanrooms

Anthony Chien of American Cleanrooms emphasizes the advantages of ULPA filters for removing small particles but points also to the disadvantages. He also points to the correlation between cleanroom class.  So, Class 1 would definitely be using ULPA filters whereas Class 7 would be using HEPAs.

ULPA filters disadvantages:




Cell and gene therapies are practices that require a high level of control. In order to fulfill their purpose and work effectively to treat life-threatening diseases, there can be no disruption in their production process - which is why theyíre usually concerned about removing smaller airborne particles between .1, .3, and .5 microns. Other cleanroom applications with less stringent requirements are typically only concerned about .5, 1, and 5 microns. This is the most important factor in determining which type of filter is best for cell and gene therapy cleanrooms. 

This also implies that most cell and gene therapy cleanrooms must meet stringent ISO standards, which are usually between ISO Class 5-7, but can be higher or lower depending on the application. For ISO 5, this means that they must have at lea 240 air changes per hour, 35-70% ceiling coverage, 40-80 feet per minute of air velocity, and no more than 10,200 particles 0.3μm or larger in a cubic meter. The requirements are a little looser for ISO 7, which requires at least 60 air changes per hour, 15-20% ceiling coverage, 10-15 feet per minute of air velocity, and no more than 1,020,000 particles 0.3μm or larger in a cubic meter.


So, which type of filter is right for your cell and gene therapy cleanroom? ULPA or HEPA? 

It depends on what specific tasks youíre hoping to accomplish within your cleanroom. Currently, in the world of cell and gene therapy, there are four main types of therapies:

         Each of these therapies requires a number of different sub-processes, which all require a different level of control. Itís best to determine which ISO standard your cleanroom needs to meet first and what size airborne particulates can be detrimental to your process, then choose your type of filter based on that.

         But from a broad perspective, ULPA filters are generally recommended for cell and gene therapy processes, since they offer more stringent control over smaller airborne particles. HEPA filters can offer enough control for some cell and gene therapy applications but arenít the most commonly recommended.