Gaseous and Particulate Contamination Guidelines for Data Centers (TC 9.9 white paper)
ASHRAE TC 9.9
This 2009 ASHRAE TC 9.9 white paper (hosted by LBNL) addresses hardware failures from copper creep corrosion and silver corrosion at sites with polluted outdoor air, especially with air-side economisers. It notes that most data centers are unaffected and that the guidance targets the minority exposed to outdoor contamination.
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Overview
On particulates, the cleanliness target is ISO 14644-1 Class 8. Filtration is set by air source: recirculated room air is filtered with MERV 8, while outside and makeup air uses MERV 11 or MERV 13. The costlier high-efficiency filter is thereby required only for air entering from outdoors. Class 8 is a relatively loose step among the ISO 14644-1 cleanroom classes.
For gases, corrosivity is limited through ISA-71.04 coupon reactivity: at severity G1, copper reactivity must stay below 300 Angstrom per month, and the 2009 edition also lists silver below 300 Angstrom per month. The measurement looks at how much a metal coupon actually corrodes rather than counting individual pollutants in the air. Copper and silver coupons are read separately because the two metals respond to different pollutants. 300 Angstrom per month corresponds to a film about 30 nm thick each month.
The humidity ceiling rests on deliquescent dust behaviour: relative humidity should stay below about 60% so that no conductive dust layer forms in a contaminated environment. The document also cites a dew point range of 5.5-15 degC with RH under 60% as the recommended envelope reference. The text dates from 2009. Later (2011) TC 9.9 guidance tightened silver to below 200 Angstrom per month, so when comparing versions the stricter value should govern. The guideline provides target values and filter ratings, not failed-hardware statistics.
Key points
- Particulate cleanliness: ISO 14644-1 Class 8.
- Recirculated room air MERV 8; outside/makeup air MERV 11 or MERV 13.
- Gaseous: ISA-71.04 severity G1, copper reactivity under 300 Angstrom/month (2009 edition also lists silver under 300 Angstrom/month).
- Keep relative humidity below about 60% to avoid deliquescent dust conductivity.
- Dew point range 5.5-15 degC with RH under 60% is cited as the envelope reference.
- 2011 TC 9.9 guidance tightened silver to under 200 Angstrom/month.
- The guidance targets the minority of sites with outdoor contamination, not most data centers.
Using it in design
- If an air-side economiser meets an urban or industrial site, prompt for corrosion coupon monitoring (G1 target) and MERV 11/13 makeup-air filtration.
- Default room filtration to MERV 8.
- Set a 60% RH maximum in humidity control.
- Where versions conflict, use the stricter silver value of under 200 Angstrom/month.
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Who should read it
Designers planning air-side economisers or specifying filtration and corrosion monitoring for sites near polluted air.
Related standards
- ANSI/ISA-71.04
- ISO 14644-1
- ASHRAE 52.2 (MERV)
- ASHRAE Thermal Guidelines
Publication details
- Authors
- ASHRAE TC 9.9
- Publisher
- ASHRAE TC 9.9
- Year
- 2009
- Document number
- TC 9.9 White Paper
- Document language
- English
- Source type
- Standard
- Access
- Free to read
- Licence
- Copyright retained; citation only — the publisher’s terms apply to the original document
Citation
ASHRAE TC 9.9 (2009). Gaseous and Particulate Contamination Guidelines for Data Centers (TC 9.9 white paper). ASHRAE TC 9.9. TC 9.9 White Paper. https://datacenters.lbl.gov/sites/default/files/ASHRAE_Contamination_Whitepaper_30_July_2009.pdf
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