Seb Doheny



Correlation Between Cleanroom Cleanliness & Air Change Rates.

Casestudy Submission:


Cleanroom cleanliness versus air change rates are poorly understood and incurring unnecessary overheads to business’.  Particle counts are the primary measure of a cleanrooms cleanliness and a key parameter when complying to ISO & FDA standards. Many cleanrooms operate far under their ISO & FDA particle count limits, instead operating to stringent internal limits.  A greater understand of the correlation between air change rates and particle counts will lead to reduce energy consumption amongst other benefits.


  • Reduced Capital Investment & Sustainable Energy Management
  • Running Cost Savings (Motor & Thermal)
  • Reduced Load on Plant Equipment
  • Increased ability to meet process requirements (temp & humidity)
  • Increased equipment capacity to serve other process’
  • Reduced non conformances & CAPA’s.
  • Carbon Credits Rebate from Energy Supplier


As a cost saving energy initiative, the Facilities Dept. at Hollister Ballina undertook a feasibility study to reduce the air change rate in the cleanrooms.  It was found that we operate well within our ISO8 limits and decreasing was not deemed a significant risk.  In conjunction with Quality Dept. it was agreed to trial the air change reduction in Cleanroom 3 first, reducing from 20 to 16 air changes.  A saving of €75k pa. was estimated from a reduction in motor speeds and thermal loadings; de-hum, re-hum, cooling, heating.

Results Achieved

  • All test and readings were within specified parameters.
  • Savings of €64,000 have been confirmed on motor load reduction ↓
  • Savings of €20,000 have been estimated on the thermal load reduction.
  • TOTAL Savings: €84,000 per annum

About Seb Doheny:

Seb Doheny holds a MSc in Energy Management, BEng in Electrical Services and is also a certified project management professional. He currently holds the function of Snr. Facilities Engineer working for Hollister ULC at the medical device manufacturing facility in Ballina.

Over the past 7 years he has projected managed multiple large capital facility / infrastructural projects such as Cleanrooms 1 & 4, office upgrades, compressor / chiller Installations & many bespoke process utilities.

He is also accountable for energy management across the site, including identifying and implementation of energy reduction projects.

Over this period he has recognised that significant capex and energy wastage is occurring in relation to cleanroom and process machine HVAC systems. The lack of knowledge, facts and statistics in relation to this area has led to excessive energy usage and increased capex on projects.

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