Measurement and quality control

The climate must be measured with average values recorded every hour and stored in plain ASCII text format. These data must be made available on request by anyone.

A running display on the institution website, with links to archived data, is the easiest way to comply.

Measuring devices must be calibrated at regular intervals which also must be identified in the data record.

The measured parameters must include temperature and relative humidity and may optionally include pollution concentrations, energy consumption, light, visitor numbers, CO₂ conc., vibration and air exchange rate.

The number of recording points must be at least one per climate zone in exhibition and storage spaces.

A zone in a non-air conditioned building is a room, or collection of rooms with approximately identical environments.

The physical and chemical state of the collection must be regularly surveyed.

Statistical sampling should be used to avoid bias. Alternatively, repeated inspection of specific marker objects. Over a long period of observation this practice of simultaneous climate and damage measurement will provide experimental confirmation for presently guessed vulnerabilities. Without this database, risk analysis is just a fashionable concept. However, the reporting of condition must be consistent between reporters.

Note that recording the deterioration of the collection is a requirement for continued accreditation. There is no other way to build up a picture of the real environmental needs of museums. Research on perfect type specimens is not enough. Museum objects are in various states of decay; their vulnerability can only be assessed by statistically secure measurement, with parallel environmental records.

Reference: Tim Padfield, 'Why keep climate records - and how to keep them', in Tim Padfield and Karen Borchersen, Editors, Museum Microclimates. Contributions to the conference in Copenhagen, The National Museum of Denmark, November 2007 pp 157 - 166
http://www.conservationphysics.org/datalog/climaterecords.pdf

Data file format

The data file shall be in ASCII code (plain text, English alphanumeric symbols). One line per measuring moment, data points separated by a space or a tab. Decimal point a full stop (.). Negative values preceeded by a minus (-). Comments lines indicated by an initial # (Unix convention)

Identifier

The comment lines should clearly explain where the measurement is taken in a way that will make sense far into the future.

Time

The ISO date-time format should be used in the archived records, whatever the format of the measuring device. Example: 2010-10-15T10:15 Note the absence of spaces, this is important to allow easy sorting and merging of data from different sources.
http://www.cl.cam.ac.uk/~mgk25/iso-time.html

Temperature

Temperature sensors are generally very reliable but all require electronic signal handling. Some battery powered temperature sensors give wrong readings when the battery voltage is low. The institution should possess one calibrated temperature measuring device, preferably using a platinum resistance sensor.

Temperature data should be recorded in degrees celsius.

Relative humidity

RH sensors drift with time. Calibration at six month intervals is mandatory. Calibration can be done in situ by comparison with a psychrometer, screened against radiation (this is important in cool places because your body heat can influence the reading). Saturated salt solutions in capsules which fit over the sensor head can also be used.