Short guidelines for the use of the MEMORI dosimeter

Transcription

1 Short guidelines for the use of the MEMORI dosimeter Introduction This guide provides advice about how the MEMORI dosimeter should be used to obtain the best information about air quality for the safeguarding of indoor cultural heritage. The advice here is a summary. More detailed information is included on the MEMORI web pages. The guide also includes the basic technical information needed to do measurements. For a more detailed description of the measurements procedure, please see the Technical user manual for the MEMORI dosimeter and reader Storage Until the dosimeter is ready for use it should be stored in its original packaging and kept dry and cool (refrigerated), as the dosimeter is temperature sensitive. Handling The dosimeter should always be handled by the hand piece; the actual dosimeter glasses should not be touched. It is essential that all the following is referring to a 3 months exposure period for the dosimeter. The risk evaluation on the MEMORI web pages is only valid for 3 months exposure of the dosimeter. For a shorter or longer exposure time a results can be adjusted to an expected 3 months exposure result assuming linearity, i.e. proportionally of the response with time. Increased deviance from 3 months exposure will give increased uncertainty in the risk evaluation. How should the dosimeter be deployed? 1. Determine the location for the three months exposure of the MEMORI dosimeter. For assistance with this see the section below, where should dosimeters be deployed? The timing of an exposure can also be important, for further information about this decision see the section, when should dosimeters be deployed? 2. Open the bag with the MEMORI dosimeter holder. 3. Take out the dosimeter (Figure 1) Always hold the dosimeter in the hand piece. Never touch the glass dosimeter chips with fingers or any other object. 1

2 Figure 1: The MEMORI dosimeter. 4. Measure the start values for the dosimeter in the dosimeter reader. (Figure 2). Remark: The start and end measurement of the same dosimeter must always be performed in the same reader instrument. 5. For more details about measurements see the Technical Manual Figure 2: Doing a dosimeter measurement with the MEMORI reader 6. The start measurement (and later measurements) are automatically stored in the reader. The start measurement (and later measurements) can be uploaded from the reader to the PC software and from the PC to the MEMORI dosimeter web pages at any time after the measurement. 7. It is recommended to upload start measurements to the PC software and to the MEMORI dosimeter web pages soon after the start measurements are performed to register the identity of the dosimeter together with a user description. 2

3 8. The barcode number for each dosimeter and the respective measurement locations and times/dates can be noted in an accompanying list for the measurements. If needed a sticker with the location identity written on it can be put on the dosimeter hand piece. 9. Mount the dosimeter on the location of interest. The mounting of replicates is usually not needed for a general location assessment. If high accuracy is needed, for example when small differences should be measured the use of replicates should be considered. Consider environmental monitoring in parallel to dosimeter deployment, for information about why this is important see the section environmental monitoring. 10. Keep the dosimeter away from strong light, extreme environmental conditions and other disturbances. The dosimeter can stand in the MEMORI stand (or something similar) (Figure 3). For an improvised stand (Figure 3) it is essential that this is not off-gassing. Assure that both sides of the dosimeter are freely exposed. Figure 3: The MEMORI dosimeter (backside) in the designed stand (left) and in a stand improvised on location (right) 11. After the 3 months exposure, take the dosimeter from the sampling location, and measure it in the MEMORI reader. Upload the results to a PC and to the MEMORI web pages (see Technical user manual for the MEMORI dosimeter and reader) 12. The dosimeter can be measured at shorter intervals (intervals shorter than 2 weeks are not recommended). The results evaluation provided for the dosimeter is however based on and ONLY valid for a 3 months exposure period. 13. For the possible exposure of the dosimeters beyond a period of 3 months, MEMORI provides no evaluation of the measured response. 14. It is recommended to note the location and time of mounting and measurement of the MEMORI dosimeter 3

4 Why measure indoor air pollution? Indoor air pollutants can cause damage to materials if present at sufficient concentrations, which vary by material and pollutant, and depending upon the environmental conditions. Some situations have a greater risk of having damaging concentrations of pollutants. Where these high-risk situations have been identified, it is recommended that the pollutant concentration is monitored in order to assess whether changes are needed to prevent damage to collections. Further information about identifying situations where risk of pollutant damage is increased can be found on the MEMORI website, along with further information about indoor air pollution, Where should dosimeters be deployed? The dosimeter measures the air quality at the exact spot where it is located. It is important to consider why the measurement is being carried out. If it is for one specific object then the dosimeter should be placed close. If the measurement is for general purposes to indicate risk, again the placement should be representative of the collection. In larger spaces this may require multiple measurements to account for potential differences. Enclosures are likely to have different atmospheres, determined by their air exchange rate, the materials present and their geometry. Air exchange rates can vary widely between apparently identical enclosures. Where enclosures are monitored it is recommended to also measure within the room. It is very rare that elevated concentrations of acetic and formic acid are measured in rooms. However, the measurement of oxidising pollutants will give a good indication of the protective effect of an enclosure. There is the potential that dosimeters placed close to emissive or absorbent materials may give biased results, this must be considered when exposing dosimeters. It is possible that exposure in this location can be valid if objects are in this position. Research investigating deployment location within enclosures has found that: In showcases generally there was no difference between dosimeters deployed in different locations. However, where there were shelves that act to separate the showcase (or enclosure) with small gaps between the door and shelf there was a difference in dosimeter response. Therefore, where separate sections are found, with potential sources or sinks of pollutants differing between the sections there is potential for different concentrations of pollutants. 4

5 Where active dehumidification is in situ this acted to equally disperse the pollutants throughout the enclosure, therefore dosimeter location had no impact. In print and picture frames there was a difference between the centre and edge of the frame for pollutants generated externally. But there was no difference for internally generated pollutants. It is therefore essential to take care with the selection of measurement location. Good choices for locations could be, depending on the purpose of measurement: Enclosures: inside showcases, picture frames, storage cases measure protection effect. Long term storage areas. Close to object of interest Location representative for general museum (indoor) atmosphere Close to ventilation from outdoor such as doors and windows, to assess expected high-risk locations. The dosimeter and holder should not be in direct contact with objects. The dosimeter glass chips should not be in contact with any object, as such contact would significantly disturb the measurement. When should dosimeters be deployed? The time of the year that dosimeters are deployed can impact upon the result. If the atmosphere in the space where the dosimeter is deployed is controlled then this is less important, but where temperature and relative humidity vary this is important. It is best to deploy the dosimeter when the response is expected to be highest, to get the worst-case scenario. Internally generated pollutants are emitted more when the temperature and relative humidity are higher. Research has shown that measured concentrations of organic pollutants are often higher in summer months compared to winter months. Temperature is also known to affect outdoor generated pollutants, generally ozone concentration increases with temperature, and nitrogen dioxide concentrations are higher in winter when temperature is low. It may be beneficial to consult local outdoor pollutant measurements. Although it is important to understand the effect that local features can have on pollutant concentrations. This is explained further on the MEMORI website. Monitored pollutant concentrations are available for sites across Europe from and specifically in the UK from It is important to consider the environmental conditions when deploying the dosimeter, and interpreting results. A tool has been developed to help 5

6 interpret the result to the maximum concentration of acetic acid possible given the maximum temperature and relative humidity; this can be found on the MEMORI website. Environmental monitoring The dosimeter is sensitive to temperature and relative humidity as are most heritage materials. The correspondence with risks for different materials is however more uncertain at RH higher than ~ 60 %. Thus, it is important to monitor these environmental conditions in addition to deploying the dosimeter. This is critical for the assessment of results and their interpretation. It may also provide useful information about risk of damage from temperature and relative humidity. 6