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Air quality measurement in depositories of the National Library of the Czech Republic – measurement methods and selected results

Summary: Preventive protection of library collections is the basis of care for their preservation. Important part of it is to ensure quality indoor air of depositories. The paper deals with climate conditions recommended for long-term preservation of library materials and their measurement in depositories of the National Library of the Czech Republic (NL CR). It concerns a measurement of physical parameters of air (temperature, relative humidity, and light) and chemical (concentration of external and internal air pollutants). Physical parameters are monitored continuously in the depositories of the NL CR, the chemical ones were measured mainly in the framework of research projects in cooperation with domestic and foreign research organizations. The Baroque Hall in Klementinum, which is the only depository of historical book collections accessible to the public during tours of the premises, was examined in particular detail regarding the concentration of pollutants.


Keywords: indoor air quality, National Library of the Czech Republic depositories, Baroque hall, Klementinum, measurement, relative humidity, air temperature, light conditions, external and internal gaseous pollutants, dust particles

Ing. Magda Součková, Ing. Petra Vávrová, Ph.D., Ing. Jan Francl / Národní knihovna České republiky (National Library of the Czech Republic), Klementinum 190, 110 00 Praha 1

Introduction

So-called preventive conservation appears as the most effective from the long-term point of view for protection and preservation of heterogeneous materials of book collections, which is a set of measures leading to prolongation of service life of book collections, or setting such climatic parameters, which will slow or stop degradation processes evoked by external degradation factors (temperature, relative humidity, dust particles, concentration of air pollutants …).  Part of preventive conservation is also production of protective cover, or box from alkaline cardboard of archive quality, and subsequent storage in depositories, where there are adjusted suitable climatic parameters for long-term storage of book collections.

Experience of the National Library of the Czech Republic with monitoring of climatic conditions in depositories over the past several tens of years, and development of monitoring methods is summarized in the paper. Brief interpretation of requirements follows for air quality for storage areas of book materials, parameters as temperature and relative air humidity, and light conditions, indoor and outdoor pollutants. Methods of air quality measurement are presented, followed by description of various types of depositories of the National Library CR. Past and present measurements of air parameters in depositories are presented in the end, as well as examples of particular results and their evaluation.

What means air

Air or atmosphere is gaseous envelopment of the Earth. It is formed of mixture of gases (78.084 % nitrogen, 20.948 % oxygen, 0.934 % argon, carbon dioxide, neon, helium, hydrogen, methane, krypton, ozone, xenon, and nitrogen oxides), and water vapour, it contains also solid and liquid particles (Leporelo, info, on line).

Required air quality (hereinafter AQ) for storage areas of book materials

The National Library CR has in its foundation documents as one of the basic subjects of its activities established protection of book documents and collections, and their preservation in good physical conditions for future generations. Most of conventional book materials is of organic origin, especially paper, parchment, binding leather, and textile, cardboard and wooden book covers, recently also plastics. Indoor air quality of areas, in which book materials are located (depositories, study rooms, exhibition rooms), markedly affects speed of their degradation, and thereby also possibility of their preservation for future generations. Physical characteristics of indoor air are important, i.e. air temperature, relative humidity, light, and chemical parameters such as content and composition of pollutants.

Recommended climatic conditions for long-term storage of archive and book materials are mentioned in standard ČSN ISO 11799 "Information and documentation – Requirements for depositing archive and library documents".

Physical parameters

Generally speaking, lowering temperature and/or decreasing relative humidity prolong service life of book materials. For paper, recommended temperature for stocking is 2–18\°C with admissible daily change ±1°C, relative humidity 30–45 % with admissible daily change ±3 %. For parchment and leather (collagen materials), temperature interval is 2–18°C with admissible daily change ±1°C, relative humidity 50–60 % and admissible daily change ±3 %. Temperature and relative humidity are the most often, and at longest monitored parameters of environment air in book depositories. In the past common thermometers and hair hygrometers were used for their measurement, which indicated current values of the parameters. Thermohygrographs with recorders already recorded temperature and humidity continuously all week long, up to a month, but it was necessary to laboriously evaluate results from the acquired graphic records. At present thermohygrometers with memory are often utilized, or cable and wireless measuring systems, data loggers (data recorders), or systems sensors, which keep results of measurement in their memory as far as to the moment of downloading to PCs. or even send directly measured values to PC, so that it is possible to respond immediately to undesirable changes of climatic parameters in depositories.

Even light markedly harms organic materials, both its ultraviolet part (UV radiation, 400–10 nm), and infrared component (IR radiation, 760 nm–1 mm). The premises should be illuminated by a sources of light without UV radiation or with eliminated UV radiation (UV filters, UV-foils). Recommended illumination level of materials of book bindings should not exceed 50 lx. For illumination in depositories, where continuous operation is not expected, approximately 200 lx above the floor level is recommended. Maximum limit for admissible ultraviolet radiation is 10 μW/lm. For measurement of light intensity luxmeters are used, or data loggers with a function of measurement of light intensity and UV/IR radiation.

Chemical parameters

Generally, pollutants are impurities in environment, which come from natural or man-made sources. They can be defined as reactive chemical substances in gaseous, liquid or solid state (particles), which can be found in environment. Pollutants are formed by both external, and internal sources.

Concentrations of external pollutants depend on local climate, geographic location, type of industry, and transport facilities, used fuel, and all that. Among external pollutants with the highest degradation effect on book materials belong sulphur dioxide and other sulphur substances, nitrogen oxides, and ozone (Hatchfield 2002).

External pollutants also contain small particles: dust and aerosols. Some of these pollutants come also from internal sources: dinitrogen tetroxide from gas ¨boilers, hydrogen sulphide from some utility materials and as human bio-waste, ozone may be produced by activities of xerox or older models of laser printers. Dust is a relatively complex pollutant, which contains particles of sizes of 1 nm–100 µm of various origin, shapes and composition (Morawska, Salthammer, 2003) Fine submicron particles (< 1 µm) contain especially soot and organic substances emitted from transport and local heating, secondary organic particles of ammonium sulphate and nitrate, and also metals from waste incineration  and industrial emissions. Particles from smoking or emitted from office equipment contribute to them also in internal environment. Coarse particles (> 1 µm) contain especially mineral particles from dust and emissions from transport and construction activities. In internal environment their source is usually cleaning, construction work, and especially visitors. They contribute especially by mineral dust brought on shoes and dresses, textile grains from clothing, and particles of dead skin. Microorganisms and mildew spores also belong to coarse particles. Various harmful effects correspond also to different origin and composition. Fine particles deposit on all accessible surfaces. Soot and organic materials cause contamination, secondary organic and inorganic particles (they were formed by reaction of primary particles emitted directly to air) may be of acidic nature and contribute to degradation of materials, often with catalytic effects of present metals (ASHRAE 2011). Secondary particles are also hygroscopic, and support thus dampening of surfaces (Seinfeld, Pandis, 2006). Coarse particles deposit only on horizontal surfaces facing upwards. Mineral particles are abrasive, and cause especially mechanical damage, particles from building activities are of alkaline nature. Deposited particles also absorb gaseous pollutants, and are suitable nutritive substrate for growth of microorganisms.

Recommended concentrations of air borne pollutants according to standard ISO/DIS 11799 are mentioned in Table 1. Units SI are given – the values are recalculated to concentrations in SI units.

 

Table 1 Recommended concentrations of air borne pollutants

Acetic acid, formic acid, and formaldehyde are the most acting internal pollutants on book materials. They are released from wood, some glues, colours, and also from proper book materials (owing to degradation of paper, acetate materials, etc.). Table 2 gives concentrations of these materials in natural environment and concentrations recommend for storage premises for collection objects.

 

Table 2 Volatile organic compounds from internal sources, which can be found inside buildings (Grzywacz, 2006)

Presence and concentration of contaminating materials can be measured directly by advanced instrumental methods (chemiluminiscence, infrared spectrometry, photometry, and the like.)1, or air samples are taken either actively by suction (Draeger tube, low-pressure cascade impactors)2, or passively. Samples are subsequently evaluated in a laboratory. For long-term measurements in depositories, passive samplers are used, which are located for a longer time in the depository (often for one month), and after it they are evaluated again in laboratory using instrumentally or visually (A-D strips, Purafil coupons, sampler Radiello, dosage meters EWO and MEMORY, etc.)3 (Součková, 2009).

Generally, to achieve higher quality of internal library air, and thus slow degradation of book materials, it is necessary to find out and nominate risks of damage of particular collection materials. Quality of internal air is necessary to determine for that. Further running measurements of climate quality is important for keeping optimum storage conditions as a precaution before speeding degradation.

Measurement of temperature and humidity in depositories of NL CR

The National Library CR located its collections in depositories in three localities. Permanent depository NL can be found in these buildings at present: Klementinum – Prague 1, Hostivař – Prague 15, and Neratovice – Central Bohemia region. These depositories are very different in their essence, no matter whether due to their location, or building type and their age.

Klementinum

It concerns a complex of historical buildings located in the centre of Prague. It originated from 16th century, and it was converted in 1930s for the needs of library. At present, the entire building of Klementinum, including depositories, passes through expansive reconstruction. In Klementinum, about two millions of books (either modern or historic) are located. Whereas it concerns a cultural memory, structural and other modifications are limited there. In the given object, air-conditioned depositories can be found (temperature and relative humidity are conditioned), in partly air-conditioned ones (only relative humidity is conditioned by the help of air *dampers), and no air-conditioned ones (neither temperature nor relative humidity are conditioned). Collections of books are located on stationary and also sliding (compact) bookshelves made of metal or wood (historic). Climatic conditions (temperature, relative humidity) are in a given object permanently monitored either by the help of wireless measuring system Hanwell, or by the help of portable thermohygrometer Commeter S 3120.

*humidifiers

Central depository Hostivař (CDH)

The depository is situated in the Prague suburb in the proximity of incineration plant of communal waste and busy automobile transport in Průmyslová Street. It concerns an object formed of a combination of a new building from 2012, and an older building opened in 1996 after *reconstruction of a manufacturing plant of a one-time state contribution organization Exhibitions from the middle of 20th century. In Hostivař, over 7 million of library collections are located (the new building – 2 millions of library collections, the converted building – 5 millions of library collections). The depositories are situated *in four stories in the new building, and *in three stories in the converted one. The deposit premises in both objects are windowless. Only air-conditioned depositories can be found in the objects (adjusted temperature and relative humidity). The library collections are placed either on mobile metal *racks (new building), or on stationary metal racks (converted building). Air temperature and relative humidity are in both objects permanently monitored by the help of wireless measuring system Hanwell.

*the reconstruction of the exhibition area

*on four floors

*on three floors

*shelves

Depository of reserve collections in Neratovice

The building erected in second half of 20th century is situated in the Central Bohemia in the suburb of Neratovice in flood areas of Elbe, and in the immediate vicinity of Spolana chemical plant. About 300 thousands of book entities were placed there. At present, sorting of collections and partial transport to other depositories is under way. Storage area, in which reserve collections are deposited, is located in three above-ground windowless stories. The depository is partly air-conditioned, only temperature is conditioned by the help of heating and ventilators. Library collections are located on stationary metal racks. Temperature and relative humidity in the depository are permanently monitored by the help of cable measuring system TQS.

Various sorts of monitoring systems and equipment

Premises, in which library collections are placed, have been and are continually monitored, and in case of need, climatic parameters in them adjusted and regulated. For climate measurement (temperature, relative humidity) in depositories, wireless measuring system Hanwell, cable measuring system TQS, and portable recording thermohygrometers Commeter S 3120 are used. For measurement of light conditions (intensity of illumination, intensity of UV radiation), portable luxmeter Hanwell ULM and combined instruments Elsec 765 C are used. For measurement of dustiness, portable instrument Casella Microdust Pro is used.

 

Wireless measuring system Hanwell (Klementinum, Hostivař)

Wireless measuring system has been installed in Klementinum since 1998, and in Hostivař since 2017, and it is continuously extended to other storage and working spaces. Wireless measuring system Hanwell is formed of sensors (thermal, humidity, light), which transmit signal (by way of amplifier) in a form of radio waves to receiver in the control unit. Here the signal is transformed to particular values, which are then saved in memory of the control unit, and the measured values are send from there to PC, with installed programme for other evaluation (graphic, tabular, statistical).

 

Cable measuring system TQS (Neratovice)

Cable measuring system has been installed in Neratovice since 2004. Cable measuring system TQS is formed of sensors (thermal, humidity), which transfer the sensed signals to a module, where they are transformed to particular numerical values and transferred to Internet network, from where it is possible to inspect and evaluate the given values (as graphs, tables) by the help of PC.

 

Portable equipment for permanent measurement of climate /recording thermohygrometers/Commeter S 3120 (Klementinum, Hostivař)

Portable equipment for permanent climate measurement (temperature, relative humidity) are deployed in storage and working premises in Klementinum and also in Hostivař depositories.

Portable equipment saves measured values in internal memory, and it is possible to download stored data and carry out evaluation (as graphs, tables) by the help of PC with installed software.

 

Portable equipment for measurement of light luxmeter Hanwell ULM and combined instruments Elsec 765 C

Portable equipment for measurement of light serves for actual measurement of light conditions (intensity of illumination, intensity of UV radiation).

 

Portable equipment for measurement of dustiness Casella Microdust Pro

Portable equipment for measurement of dustiness serves for actual measurement of dustiness.

Measurement of air borne pollutants in depositories NL CR – examples and results

In addition to already performed routine measurements of temperature and air dampness, and light conditions in depositories NL CR, measurements of air borne pollutants have been and are as well as at present in progress in selected localities of these depositories.4

The first measurements of air borne pollutants were performed by the Czech Hydrometeorological Institute (ČHMÚ) in years 1991–1992, further in years 2006–2007 as a part of research programme of the Ministry of Culture "Research and development of new procedures in protection and preservation of precious written memories", which was solved in the National Library in years 2005–2011. It was thus possible to compare changes in pollutant concentrations after 15 years. Measurements were carried out using mobile measuring vehicle on the economic yard in premises of Klementinum (outdoor environment), and at the same time using separate measuring instruments for determination of SO2, NOx and O3 in depository of the Department of manuscripts and old printings – DMOP (internal environment). It concerned direct air analysis. It was found that quantity of SO2 in outdoor air compared to year 1992 significantly dropped (roughly six times), concentration of NOx increased both in external and internal environment of Klementinum, and ozone concentration in store room dropped compared to year 1991.

Measurement of concentration of air borne pollutants by direct air analysis is expensive, and therefore, several types of passive samplers were used for other measurements.

Indicator coupons Purafil are plastic bands half coated with a layer of silver, and half coated with a layer of copper, which may be located to environment under examination, and left there for a period of 30–60 days (Purafil 2020). It results in a layer of rust, which will be evaluated in laboratories of company Purafil, and its increase found out for a specific time interval. According to increase of a corrosive product, the monitored environment will be categorized to one of five classes of air cleanness. In depositories of NL CR, coupons were deployed in Klementinum (Slavonic library, so-called Fantovka, Baroque hall, Treasury DMOP, former Klementinum Gallery and cellar), in the depositories in Neratovice and in CDH in ground floor of the central store and in the store room of microfilms. Exposed coupon were evaluated in class C1 and C2, i.e. as fully clean and clean air, only room of Treasury DMOP was ranked to class C3 – medium air cleanness.

Other air quality measurements in NL CR were carried out using dosimeters EWO-G. This type of dosimeter was developed within the frame of European research project MASTER – Preventive Conservation Strategies for Protection of Organic Objects in Museums, Historic Building and Archives (CORDIS 2005). Measuring section of the dosimeter consists of glass platelet coated with a film of organic polymer of constant thickness. The polymer reacts with surrounding environment and becomes less transparent. The change is expressed as change in UV absorption at 340 nm measured using a spectrophotometer. Exposure time is three months, and after evaluation, tested environment is again ranked to classes 1–5. In premises of the National Library CR, four dosimeters in all were deployed. In Klementinum, measurements were carried out in the Treasury room DMOP, in th Baroque hall, and inside display case in former Klementinum Gallery. The last dosimeter was placed in the Central depository Hostivař in storeroom DMOP. The best quality of environment – Class 1, which indicate environment suitable for archives, was also found there. Remaining three measured environments rank to Class 2: suited rather for the needs of museums than depositories for long-term storage. The display case and the Treasury room DMOP at the same time approached Class 1 – suitable for archive storage, while the Baroque hall already was at the upper limit with Class 3 – unsuitable for storage.

Other type of samplers, which were used for measuring gaseous pollutants in depositories of NL CR, and till today they monitor concentration of sulphur and nitrogen oxides in the Baroque hall, are passive samplers of company SVÚOM. In years 2007–2008 they were placed in premises of Klementinum in nine measuring sites (depositories and study rooms), and in CDH on three measuring sites, both indoor and outdoor. The samplers were exposed for one month, and then evaluated in laboratory of SVÚOM.

Identified concentrations of SO2 in outdoor environment of Klementinum and Hostivař were comparable. Concentrations found in individual internal standpoints highly fluctuated. The highest values in Klementinum were found in the Baroque hall (entering of visitors), and in manuscript study room (opening of windows). In Hostivař, outdoor concentration of SO2 was higher than concentration in store room.

Concerning nitrogen oxides, large quantities are produced by automobile transport. One of samplers for measuring external concentrations of NOx was placed in Křížovnická Street at the level of 2nd floor, nevertheless, the values measured with it were higher than values of a sampler placed between ground floor and 2nd floor on courtyard of Klementinum. Values measured in CDH were lower, which again is connected with the building location. Values of NOx in depositories in CHD and in Klementinum are comparable and lower than the values in others premises of interest, routinely accessible to workers and visitors of the National Library CR.

Passive samplers of company SVÚOM have been used since 2012 for continuous measurement of concentration of sulphur and nitrogen oxides in the Baroque hall – Fig. 1.

 

Fig. 1 Measurement of NOx concentration in the Baroque hall in period 2012–2018 (μg.m3)

Research project "Monitoring and evaluation of internal environment in the Baroque hall of NL CR", supported by Norwegian funds dealt with evaluation of quality of internal environment of the Baroque hall in Klementinum, which serves partly as depository of historical collections, and partly as a section of visit route for public. The Health Institute with a seat in Ústí nad Labem carried out measurements of content of internal pollutants, VOCs (volatile organic compounds) in particular, in the Baroque hall and adjacent premises (a total of five sampling sites, including outdoor air) in July and November 2009, see Fig. 2. Air samples were collected, which were subsequently analysed in laboratory.

 

Fig. 2 Concentration of acetic acid in the corridor next to the Baroque hall and in adjacent depository (μg.m-3), active sampling, the Health Institute

Found concentrations of acetic acid, especially in closed areas of the depository, highly exceeded the recommended values (Table 3).

Table 3 Concentrations of formic and acetic acids in the Baroque hall, as measured by passive sampler NILU

High concentrations of acetic acid measured by the Health Institute are confirmed by the results of measurement of Norwegian Institute for Air Research – NILU, a partner of the project of Norwegian funds (Table 3).

Other partner of this project of Norwegian funds was the Institute of chemical processes of the Academy of Sciences CR (ÚCHP), which specializes on measurement of air quality in term of concentrations of dust particles and carbon dioxide. It carries out also chemical analyses of particles and measurement of gaseous pollutants using passive samplers. In a link to the study of air quality in the Baroque hall carried out with the use of the grant of Norwegian funds before reconstruction of the hall (2011), ÚCHP elaborated a comparative study in late 2017, which ought to find out, how air quality changed after reconstruction. In measurement in 2008, the Baroque hall was a part of visiting route, and tourists entered it. Measurement of concentrations of dust particles showed that presence of visitors increased concentration of particles up to six times. Increase in concentrations always started with entry of the first visitors, and reached a maximum at the end of opening hours. Particles concentration then gradually dropped to original values owing to their deposition on accessible surfaces (Fig. 3). Identical time course exhibited concentrations of carbon dioxide exhaled by visitors (Fig. 4).

 

Fig. 3 Time course of numerical concentration of coarse particles of size faction 2.5–20 µm in internal environment of the Baroque hall during measurement in 2008 (Smolík, 2018)

 

Fig. 4 Time course of concentration of carbon dioxide in internal environment of the Baroque hall during measurement in 2008 (Smolík, 2018)

During measurements in 2017, which were carried out already after reconstruction of the hall, change in opening hours occurred, in the first phase hall was still closed for public (13th Oct. - 13th Doc. 2017), and in the second phase (14th Dec. 2017 -  21st Jan. 2018) visits were already under way. It made possible to find out, to what degree visits affected air quality in the hall. External and internal concentrations of fine dust particles of fraction 0.3–1 µm are compared in Fig. 5. It can be seen from the figure that internal concentrations imitate the external ones, but they are markedly lower, and also that the presence of visitors (opened for visits in 14th Dec.) had virtually no effect on concentrations of fine particles.

 

Fig. 5 Time record of external (outdoor) and internal (indoor) concentrations of fine dust particles of fraction 0.3–1 µm (Smolík, 2018)

Time courses of external and internal concentrations of particles of fraction 1–2,5 µm are compared in Fig. 6. It can be seen from the figure that external air had very small influence on internal concentrations, because most of particles of this size was almost quantitatively captured by the buildings mass.

 

Fig. 6 Time record of external (outdoor) and internal (indoor) concentrations of dust particles of fraction 1–2.5 µm (Smolík, 2018)

 

Fig. 7 shows comparison of external and internal concentrations of coarse particles of fraction 2.5–10 µm. A pronounced effect of visitors, observed also in previous study in 2008, is perceptible from the figure.

 

Fig . 7 Time record of external (outdoor) and internal (indoor) concentrations of coarse dust particles of fraction 2.5-10 µm (Smolík, 2018)

Conclusions

Measurements of air quality on various levels have been and are in progress in depositories of NL CR . The basis is measurement of relative humidity and air temperature in all types of depositories. The depositories in Hostivař and Neratovice are not equipped with windows, light conditions are then necessary to be monitored preferentially in depositories in the historic building of Klementinum. In the new building of the depository in Hostivař regulation of climatic parameters is at very good level, and only check of possible variations or accidents is desirable.

Most information was found on air quality in the Baroque hall on the premises of Klementinum. It is given by the fact that it concereds both the depository of historic book collection, and the area incorporated into sightseeing route, and therefore accessible to public, even though only in limited extent. The Baroque hall is certainly also an attractive area in light of its historic value. Concentrations of external pollutants (SO2, NOx), internal pollutants (acetic acid), and dust particles were also monitored there. Just measurements performed in the Baroque hall show that entrance of a larger number of persons has a negative influence on air in the depository, and therefore also on condition on historic collections deposited in it.

The paper summarises information gained for several tens of years of monitoring of climatic parameters in various types of depositories in various types of buildings in the National Library of the Czech Republic (NL CR). This summary should serve for inspiration to libraries, how to monitor air quality in depositories, and how so-called preventive preservation minimizes damage of book collections. The costs on preventive preservation are in a result much lower than afterwards costly restoration of damaged pieces.

Acknowledgments

This paper was prepared within the frame of institutional support of the National Library of the Czech Republic by the Ministry of Culture CR as a research institution (IP DKRVO), Section 7: Protection of library collections.

References

ASHRAE, American Society of Heating, Refrigerating and Air-Conditioning Engineers, Inc. 2011. Heating, Ventilating, and Air-Conditioning Applications SI Edition, Part 23. Museums, Galleries, Archives, and Libraries, 1791 Tullie Circle, N.E., Atlanta, GA 30329, 2011, ISBN 978-1-936504-07-7.

CORDIS, 2005, available from: https://cordis.europa.eu/project/id/EVK4-CT-2002-00093

ČSN ISO 11799 „Informace a dokumentace – Požadavky na ukládání archivních a knihovních dokumentů", 2006, s. 8–9 (Czech standard ČSN ISO 11799 "Information and documentation – Requirements for deposition of archive and library documents", 2006 pp.8-9(.

ĎUROVIČ, Michal et al. Restaurování a konzervování archiválií a knih. Vyd. 1. Praha: Paseka, 2002. 517 s. ISBN 80-7185-383-6  (in Czech: Restoration and preservation of archival documents and books. 1st edition, Prague, Paseka, 2002, p. 517. ISBN 80-7185-383-6).

GRZYWACZ, C. M., Monitoring for Gaseous Pollutants in Museum Environments, 2006, s. 110. ISBN13: 978-0-89236-851-8.

HATCHFIELD, Pamela. B., 2002. Pollutants in the museum environment. Archetype Publications Ltd., ISBN 1-873132-96-4.

Leporelo.info Atmosféra (Air) available on: https://leporelo.info/atmosfera.

MORAWSKA, L. a T. SALTHAMMER, 2003. Indoor Environment: Airborne Particles and Settled Dust. New York: John Wiley and Sons. ISBN 978-3-527-30525-4.

PURAFIL, 2020, available on: https://www.purafil.com/products/monitoring/passive-monitoring/

SEINFELD, J. H. a S. N. PANDIS, 2006. Atmospheric Chemistry and Physic, second edition. Hoboken: John Wiley and Sons. ISBN 978-0-471-72018-8.

SMOLÍK, J. Kvalita ovzduší v Barokním knihovním sále Národní knihovny v Praze, Klementinum, zpráva 2018, ÚCHP AV (in Czech: Air quality in the Baroque library hall of the National Library in Prague, Klementinum, report 2018, ÚCHP AV).

SOUČKOVÁ, M. Měření polutantů v Národní knihovně České republiky, XIV. Seminář restaurátorů a historiků, Brno 2009, ISBN 978-80-7469-007-5 (in Czech: Measurement of pollutants in the National Library of the Czech Republic, XIV. Seminar of restorers and historians, Brno 2009, ISBN 978-80-7469-007-5).

SOUČKOVÁ, Magda, Petra VÁVROVÁ, Jan NOVOTNÝ, Jana DŘEVÍKOVSKÁ, Hana PAULUSOVÁ, Benjamin BARTL, Lenka BARTLOVÁ, Bronislava BACÍLKOVÁ, Roman STRAKA, Michal ĎUROVIČ, Ludmila MAŠKOVÁ a Jiří SMOLÍK.. Památkový postup „Zlepšení kvality vnitřního ovzduší knihoven a archivů s cílem významně omezit degradaci knihovních a archivních materiálů" NK ČR. 2015. (in Czech: Conservation procedure "Improvement of internal air quality in libraries and archives with the aim of significantly limit degradation of books and archive materials"). Available on: http://www.nusl.cz/ntk/nusl-260952.

Foundation document of the National Library of the Czech Republic, p. 2, available on: https://www.nkp.cz/soubory/ostatni/zrizovaci-listina-nk.pdf.

SOUČKOVÁ, Magda, VÁVROVÁ, Petra a Jan FRANCL. Měření kvality ovzduší v depozitářích Národní knihovny České republiky – metody měření a vybrané výsledky. Knihovna: knihovnická revue, 2020, 31(1), ..... ISSN 1801-3252 (in Czech: Measurement of air quality in depositories of the National Library of the Czech Republic – Measurement methods and selected results. Library: Librarian review, 2020, 31(1), ..... ISSN 1801- 3252.

Foot notes

1 Chemiluminiscence – measurement of light energy emitted in a result of chemical reaction infrared spectrometry – measurement of emission or absorption spectra, wave length of which falls to the region of infrared radiation.

Photometry – spectroscopic analytical method of measurement of light energy absorption by the help of photometers with visual detection.

2 Details on mentioned methods in the Conservation procedure "Improvement of internal air quality in libraries and archives with the aim of significantly limit degradation of books and archive materials"). Prague 2015, available on: http://www.nusl.cz/ntk/nusl-260952

3 See note 2

4 Pollutant – a material polluting a certain environment, in our case depositories, or their external neighbourhood.

Draeger tube: designation of a detection tube – trade name, the tubes are used for detection of selected chemical substances, and are designed for orientation determination of harmful gases in air (e.g. oxides of sulphur and nitrogen, ozone etc.).

Passive samplers: Air analysis may proceed either directly, or obtained samples may be analysed. Sample collection is carried out passively or actively. Passive samplers requiring laboratory analyses are simpler for routine measurements. The user only exposes the equipment, seal it, and send it for analysis. Analytical laboratory determines volume of tested air, amount of detected pollutants, and calculates concentrations. In most directly readable samplers the user must take into account duration of exposure, compensate it to deviation from standard duration of exposure, and determine concentrations of pollutants according to colour changse. Because reading of colours is subjective, it may be a source of inaccuracy in results, an experience operator minimizes this problem. Price of passive samplers is relatively low. Qualitative directly readable passive samplers (coupons) are easier for use, less complicated, and cheaper than quantitative laboratory analysable equipment (open-path diffusion tube). Lower accuracy as compared to laboratory analyse may be sufficient for confirmation of polluted environment.

Low-pressure cascade impactors: They serve for determination of size distribution of mass concentration and chemical composition of particles, e.g. of type Berner; they separate particles to ten size fractions. Obtained samples are analysed by gravimetry, ion exchange chromatography (water soluble ions), and PIXE method (Particle Induced X- ray Emission, determination of elements).

A-D strips are coloured paper strips – indicators, which detect and measure relevance of so-called acidity syndrome in film pads or photographic materials manufactured from cellulose acetate. These strips inserted into box with films or negatives change colour according to the extent of acidity – with higher acidity strips change colour from original blue to green-blue, green, green-yellow, up to brightly yellow. The result is determination of damage intensity or degree of degradation of acetate films or negatives, and suitability or unsuitability of their present storage.

Coupons Purafil: filtration material Purafil Select Chemisorbant removes sulphane, sulphur dioxide, dinitrogen tetroxide, and formaldehyde from air. It is formed of ball-shaped, porous granules. The granules are manufactured of aluminium oxide and a bonding agent impregnated with potassium permanganate, which oxidizes gaseous pollutants and thus removes them permanently from environment.

Sampler Radiello is a commercial equipment or a personal monitor (badges), and varies from tubes by geometry. Active surface is closed in a plastic or teflon cover, and physical diffusion barrier is placed 1 mm up to 1 cm above the active surface. It concerns adsorption filling and diffusion body of porous polyethylene of various thickness, porosity, and pore sizes), manufacturer Radiello, Sigma-Aldrich, 2006.

Dec 19, 2020