Humidity - Metrology Lab Environment

Try a search for clean rooms. it should be similar for metrology.

I found this for you with a link to a manual with some standards... hope it helps you!

Metrology Lab

The National Metrology Institute (NMI).

(Traditionally referred to as 'the national laboratory').

Metrology - The science of measurement.

Environmental control is not difficult if it is correctly planned and installed but is a nightmare to fix if you try to patch it up after the main installation is complete. Most of the laboratories will require a temperature control of 23 °C ± 2 °C for high level work and ± 5 °C for general purpose work. Traditionally, the dimensional laboratories have worked at 20 °C and sometimes require a tighter spec of ± 1 °C. It is, however, better to have a good stable temperature than the ideal set point. What is of equal importance is the temperature profile of the whole laboratory. The correct use of diffusers will spread the conditioned air evenly around the laboratory so that there are no direct draughts over any specific work space. Humidity control is of less importance but needs to be maintained at around 45% ± 10% RH.

This manual is designed such that it follows the sectional format of the American National Standard for Calibration, ANSI/NCSL Z540-1-1994. Each section of the manual is aligned with that of the corresponding section in the ANSI/NCSL Z540-1-1994 standard. The last section of the manual consists of an annex containing the policy statements of MMC Metrology Lab

http://www.mmc.ws/qm/QM1.pdf

I am grateful for your efforts, however, the Z540, NMI, or clean room is not the type of environment I'm accustomed to working in. To low humidity creates static, to high creates rust. I'm observing rust on precision equipment, although humidity in our lab is currently running at 45-50%. I remember a document many years ago working in another metrology lab at recommended humidity settings but have yet to rediscover it. I currently have request in with NIST and a few other nationally know metrology labs but either they are extremely busy or they themselves can't find documentation. My reasons in needing this document is evidence for upper management in order to make changes with our current system.

I think your looking for the old MIL( MIL-STD-45662A ) that was replaced by the with NCSL/ANSI standard Z540-2-1997 ANSIZ540-1-1994 or ISO 17025. I think you can aquire it thru the Standardization Document Order Desk. If it was not the weekend I would ask the good Doctor who runs our lab for a copy...but I will probably have to wait till Monday.We have all the mil docs as we produce millitary aircraft. You can also try the link below.

NOTICE OF CANCELLATION: MIL-STD-45662A
NOTICE 2: February 27, 1995
SUPERSEDING NOTICE 1: 20 January 1995

MILITARY STANDARD
CALIBRATION SYSTEMS REQUIREMENTS

MIL-STD-45662A, dated 1 August 1988, is hereby canceled. Future acquisitions should refer to International Organization for Standards (ISO) 10012-1, "Quality Assurance Requirements for Measuring Equipment," Part 1: "Meteorological Confirmation System for Measuring Equipment;" American National Standards Institute (ANSI)/National Conference of Standards Laboratories (NCSL) Z540-1, "General Requirements for Calibration Laboratories and Measuring and Test Equipment;" or comparable standards as alternatives to MIL-STD-45662A.

(DOD activities may obtain copies of ISO 10012-1 and ANSI/NCSL Z540-1 from the Standardization Document Order Desk, 700 Robbins Avenue, Building 4D, Philadelphia, PA 19111-5094. The private sector and other Government agencies may purchase copies from the American National Standards Institute (ANSI), 11 West 42nd Street, New York, NY 10036.)

For the someone who still asks about the old military standards the following link may help.
http://www.dtic.mil/ and http://www.dtic.mil/stinet/str/

I suggest you approach this problem from a science as well as a specification standpoint. 50% RH should not encourage static or rusting. If you have equipment rusting at 50% RH, consider the possibility that the surface temperature of the equipment may be below the dew point of the ambient air. If this is the case, you have a special problem that may require an unusual solution. Rusting should not be a problem below 75% RH unless you have contamination on the surface.

If you look long enough you are bound to find a document that supports your point of view. That doesn't make it correct. 45-50% RH will NOT promote rusting of steel UNLESS you have salts or other contamination caused by fingerprints, etc.

Try Army Technical bulliten TB750-25

relative humidity setting in metrology labs

"Such enclosed areas, often designated as metrology laboratory rooms, provide continued exchange of air in a uniformly ... The introduced air is filtered and dehumidified (relative humidity maintained at a level of 35% to 45%)"

"a gear metrology laboratory was established, having temperature controlled closely at 20 °C and a relative humidity of less than 50 percent"

"metrology laboratory has constant temperature and humidity, and is dust- free. Such controlled conditions are ... Relative humidity of the room is maintained at the 45 to 50 percent level. The low humidity ..."

Email stricklandga@ornl.gov

The ORNL Metrology Laboratory (ORNLML) maintains a variety of temperature and humidity standards traceable to SI (International System of Units) through the National Institute of Standards and Technology (NIST) and other international primary laboratories. These standards generate and measure various temperature and relative humidity properties required to perform traceable calibrations of our customers' instruments and equipment. ORNLML can provide accredited calibrations for any temperature and relative humidity parameters within the ranges detailed in our Scope of Accreditation. However, traceable non-accredited calibrations are available for temperatures outside of our Scope of Accreditation. The tables below list our accredited capabilities. Our Scope of Accreditation includes complete details of our accredited capabilities.

Excellent Markar! The page from Farago/Curtis will help support my contention. I still believe there is a document out there distributed by either Federal or Military that specifically targets lab environments, more than likely it's a cancelled document. I familiar with Oak Ridge, they do great work and because so I've referred many clients to them. Thanks again, it has always been my belief to maintain a lab's humidity between 35% and 45%. It never dawned on me to see what Farago/Curtis had to say about it.

InspectorK, have you contacted the makers of the equipment in question? Equipment sometimes has environmental recommendations in the 'Installation' part of the equipment manual. Or you could contact a local university whose engineering department should have some ideas.

Logan

NCSLI RP-7 Laboratory Design states "Dimensional measurements require an upper limit in humidity primarily to prevent corrosion of iron based metals. This is usually set at less than 50%. A lower humidity limit of 20% is set for control of electrostatic discharge and for personnel comfort."

The book "Corrosion in the Petrochemical Industry" edited by Linda Garverick states on page 5, for iron, the critical RH appears to be about 60%, but water begins to adhere to a polished metal surface at an estimated 55% RH, forming a film.

For these reasons, I would recommend 20%-50%RH for your lab operations and oil down your metal standards if your environmental control exceeds 55%RH.