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Figure 4. The concentration of outdoor generated ozone and indoor generated acetic acid as a function of the air exchange rate. (Reproduced with permission from Ryhl-Svendsen et al.*?). — Figure 4 The concentration of outdoor generated ozone and indoor generated acetic acid as a function of the air exchange rate. (Reproduced with permission from Ryhl-Svendsen et al.*?).

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The results from the laboratory and field measurements in Part I-III are summarized in Chapter 4. All data is collated into a Monte Carlo simulation in Chapter 5. The simulation examines the concentrations of formic acid and acetic acid in indoor air, and determine the fraction of organic acids that is removed through active air filtration and the fraction that deposit back onto interior surfaces. Chapter 6 contains a discussion of the methods used to control organic acids in storage buildings and their energy use. Finally the thesis ends with a conclusion in Chapter 7. Figure 1. Graphical outline of the thesis.

Figure 2. Sketch of the new storage facility using semi-passive climate control belonging to the National Museum and the Royal Library of Denmark. (© Drawing by Gottlieb Paludan Architects from https://www.gottliebpaludan.com). Large investments are now being made in heritage institutions to improve the preservation conditions in storage buildings and reduce the energy use. Examples of major storage buildings under construction in Denmark include the shared storage facility between the National Museum and the Royal Library (Figure 2) and the shared storage facility between local museums in Senderjylland (Figure 3).

Figure 3. Sketch of the new storage facility using semi-passive climate control belonging to Museum Sonderjylland. (© Visualisation by Friis & Moltke Architects and BASE Erhverv from https://www.faod.dk/friis-moltke-vinder-konkurrencen-om-magasinbygning/).

rhe concept of passive climate control is to build an airtight hygrothermal inert building envelope on an un nsulated concrete floor. The building envelope will even out daily fluctuations in the outside climate. The un nsulated concrete floor will act as a heating surface in winter and a cooling surface in summer (Christense! ot al., 2016, Padfield et al., 2018). As the storage is unoccupied, no heating to comply with human comfor ‘equirements is needed. Simulations using COMSOL Multiphysics® modelling software have shown that thi emperature in a storage building with passive climate control changes slowly from 7°C in winter up to 15°C nm summer in a temperate climate as Northern Europe (Figure 4) (Padfield, 2013). Smedemark et al. (2019a neasured a temperature from 7°C in winter up to 19°C in summer in a storage building with passive climat control in Denmark. Figure 4. Computer simulation of the temperature in a storage building with passive climate control during winter and summer in a temperature climate as in Northern Europe. (Reproduced with permission by T. Padfield (2013) based on a simulation by Bohm and Ryhl-Svendsen (2011) using the COMSOL Multiphysics® Modelling Software).

A widespread concern in connection with the application of semi-passive climate control is that the airtight building envelope in combination with emissive collections stored densely packed on movable shelves can lead to thermal stratification and a local accumulation in indoor air pollution. Figure 5 show general museum collections stored densely packed on movable shelves in a large storage room at the shared storage facility with semi-passive climate control at the Centre for Preservation of Cultural Heritage in Vejle, Denmark. Figure 5. A storage room with semi-passive climate control at the shared storage facility at the Centre for Preservation of Cultural Heritage in Vejle, Denmark. The store contains general museum collections stored closely packed on movable shelves with a large amount of collection materials in a small space.

Figure 6. Storage I seen from the outside (left). The store contains a book collection stored on compact movable shelves (right).

Figure 7. Floor plan for Storage I. The areas with movable compact shelves are marked in grey. A HVAC system with heating, cooling, humidification, dehumidification and air filtration service the storage ‘oom (Supplementary information 1). The HVAC system contain F8 particle filters as well as two consecutive activated carbon filters. A building management system (BMS) control the intake of outdoor air, the internal recirculation rate and the climate conditions. Air is supplied to the storage room to maintain a constant overpressure and reduce infiltration from outside.

Figure 8. Storage II seen from the outside (left) and the room with a mixed material collection stored on compact movable shelves seen from the inside (right).

information 2. Light sensors are activated when the storage rooms are in use. The storage room with a paper-based archival collection has two external walls as well as one wall facing a central hall and one facing another storage room. The storage room with a mixed material collection has one external wall, one wall facing a central hall and two walls facing other storage rooms (Figure 9). The entrance has a double door airlock. A detailed description of the wall construction is given in Supplementary information 2. Light sensors are activated when the storage rooms are in use. Figure 9. Floor plan for Storage II. The storage room with a paper-based archival collection is on the right and the room with a mixed material collection is on the left. The areas with movable compact shelves are marked in grey.

Table 1. Information about Storage I and the two rooms in Storage II. The information is collected in Table 1.

Table 2. The Monte Carlo simulation model parameters and input data. The Monte Carlo simulation ignores the contributions of formic acid and acetic acid from construction materials, building interior and people’s activities. The simulation only accounts for the formic acid and acetic acid emissions from heritage collections.

Table 3. The nine scenarios modelled in the Monte Carlo simulation. distribution was therefore assigned to each variable in this study. 5.3 Results and discussion

stored on wood packaging. Figure 10. The Monte Carlo simulations prediction of the formic acid and acetic acid concentrations in a storage building with a mixed material collection at normal indoor room conditions.

Figure 11. The Monte Carlo simulations prediction of the formic acid and acetic acid concentrations in a storage building with a mixed material collection stored on wood packaging at normal indoor room conditions.

Table 4. The minimum and maximum organic acid concentration predicted in the Monte Carlo simulations for the nine scenarios. The 95% quartile and the average concentration predicted together with the standard deviation are also given. All nine probability density plots have a similar shape. They are all clearly right skewed. To exclude extremely unlikely high concentrations the 95% quartile were used as the maximum concentration expected. Table 4 show the average predicted concentrations and the standard deviation. The average concentration indicates where the distribution is centered. The standard deviation show the large concentration interval obtained from the Monte Carlo simulations and thereby the uncertainty in the predictions.

Figure 12. The average organic acid concentration predicted from the Monte Carlo simulations together with the standard deviation.

zero. All negative values were therefore set to zero. The surface removal rate probability density plots predicted in the Monte Carlo simulations are highly right skewed and to exclude extremely unlikely values the 95% quartiles were used as the maximum rate. The Monte Carlo simulations also predict scenarios where the source strength is lower than the air exchange rate giving rise to a negative surface removal rate. This is a model error as the surface removal rate can never be below zero. All negative values were therefore set to zero. Figure 13. The Monte Carlo simulations prediction of the surface removal rate in a store with a mixed material collection at normal indoor room conditions. The collection is stored on wood packaging.

Figure 14. The Monte Carlo simulations prediction of the surface removal rate in a store with a mixed material collection stored on wood packaging at normal indoor room conditions with active air filtration.

Table 5. The simulated surface removal rate of formic acid and acetic acid onto interior surfaces in a room with a paper and a mixed collection.

Layout of the ventilation system in Storage II. The system only contains internal dehumidification and a heating surface used only to dry out the building after construction. Layout of the HVAC system in Storage I with heating, cooling, humidification, dehumidification and air filtration.

All exterior walls in Storage I (left) have a glass facade while the interior walls of the storage area consisted of 180 mm concrete, 200 mm insulation, a vapour barrier, 50 mm insulation, 300 mm air gab and 40 mm concrete. \ll exterior walls in Storage I (left) have a glass facade while the interior walls of the storage area consisted A detail showing the construction of the interior and exterior walls in Storage I and II.

Figure 1: A state-of-the-art storage facility in the region Vejle, Denmark, for general museum collections with semi-passive climate control. What is noticeable is how the facility consists of large storage halls with museum collections stored closely packed on mobile shelving with a large loading of collection materials in a small space. Collections made of diverse materials are stored together.

Figure 2: Computer simulation of the temperature in a repository with passive climate control. The building is constructed with a well-insulat- ed building envelope with high thermal inertia placed on an uninsulat- ed concrete floor. Based on outside climate conditions in Denmark the simulation show a winter scenario where the temperature fluctuates from down to 7°C in winter (left side) up to 15°C in summer (right side). (Reproduced with permission by T. Padfield*4 based on a simulation by Bohm and Ryhl-Svendsen%? using the COMSOL Multiphysics® Modelling Software).

Figure 3: Concentration of carboxylic acids in heritage institutions as reported in literature. At the top diagram and displayed as sum of total carboxylic acids: inside a microclimate frame (yellow), display cases and cupboards (red), repositories (blue), and exhibitions (grey). Please note log scale, which is used due the large span of reported values. The bot- tom diagram zoom in on the observations from repositories and dis- plays the fractions of formic and acetic acid concentration. Only obser- vations of concentrations above the detection limit are included. In cases where a concentration was given as a range, the highest con- centration value is used. Numbers on x-axis gives the literature refer- ence. If (*) the concentration value was given as ug/m: in the original reference, but converted to ppb by this author.

pollution in archives, which directly can be attributed to the collection itself. This was performed under laboratory conditions, at which the environmental conditions were controlled to mimic winter and summer indoor climate scenarios (10°C and 22°C).

Table 1 The characteristics of the six paper samples. pH values with an asterisk were determined with own measuring according to TAPPI T509 and differed slightly from the manufacturer’s specifications. Two papers are modern standard test papers produced by Klug Conservation (Immenstadt, Germany): Novo Test Paper 1 contains mechanical wood pulp including 17% lignin, and Novo Test Paper 2 is a wood-free paper made from 100% bleached cellulose pulp. The four other samples are naturally aged historic papers, covering a period of almost 70 years of the 19th and 20th century. They originate from a test sample collection of the Royal Library in Denmark. The exact composition of the historic papers was not established, except for the presence of lignin, which was identified by the phloroglucinol spot test (TAPPI T401, 1992). The aqueous cold extract pH of the samples was Six paper types were selected to represent the variation of paper types found in a typical library collection.

FIGURE 2 A passive diffusion sampler for formic and acetic acid mounted on an aluminum rack with a metal spring clip.

FIGURE 3 The test chamber set-up. Clean air was conditioned by splitting the air stream in two, and bubbling one part of it through a washing bottle with water. The conditioned air was then supplied to the temperature controlled test chamber. The chamber’s exhaust air was passed through two impingers with an alkaline solution to collect formic acid and acetic acid from air. The emission of formic acid and acetic acid from the papers were collected in a 2.9 L glass test chamber (desiccator jar), which was ventilated continuously with clean air at a rate of 8 chamber volumes per hour. with clean air at a rate of 8 chamber volumes per hour.

Table 3. Mass-specific emission rate of paper samples from climate chamber measurements, in ng acid emitted per gram of paper, per hour, at normal room temperature, cool, and at dry conditions. The values given are the average of two measurements, plus-minus one standard deviation.

FIGURE 4 Mass-specific emission rate at 22°C and 50% RH, and the pH (aqueous cold extract) of each paper sample. Each data point represents the mean value of two replicate tests.

FIGURE5 The mass-specific emission rate of the paper collections at the three storage sites, at summer and winter temperature conditions. The surface removal rate was for all locations estimated to be 2 per hour, and the ventilation rate 0.1 per hour, except for Koppel, which was 0.6 per hour. The data point in brackets indicates samplers exhausted, and that level might have been higher. The lines connecting data points are for visual aid only.

Table 1. Description of the eight samples. *Sample no. 1 was dated based on watermark identification. **The archaeological wood was treated with PEG from October 2013 to July 2016 and then freeze-dried from August 2016 to January 2017. The area-specific emission rates of formic acid and acetic acid were quantified for four naturally aged paper samples (samples no. 1-4) together with two naturally aged wood samples (samples no. 5-6) and a newly produced wood packaging (sample no. 7) used to transport and store heritage collections in storage buildings. As an example of a well-known highly emissive material, the acetic acid emission from a cellulose acetate photographic negative (sample no. 8) was measured as well (Table 1).

Table 2. Surface area, mass and loading factor of sample 1-8. 2.2.2 Active air sampling and analysis

Figure 1. Area-specific emission rates of formic acid and acetic acid from sample 1-7 at 20% RH and constant temperature (23 +2°C) as well as at 10 and 23°C with constant RH (50 +5% RH). The cross indicates measurements that are below the LOQ of 5 ug m*. A few authors have measured the emission rate from paper. Ramalho et al. [3] measured a mass-specific emission rate SERm (mass emitted per gram material, per hour) of acetic acid from paper at indoor conditions after accelerated ageing. The mass-specific emission rate was 887 ng g! h'! from a cotton rag paper and 4820 ng g! h'! from a paper made of ground-wood pulp. Smedemark and Ryhl-Svendsen [20] measured the mass- specific emission rate of formic acid and acetic acid from four paper samples from the late 19" to the 20" century at indoor conditions. The emission rate in their study ranged from 45 ng g' h"' from a book printed in 1864 up to 468 ng g' h'' from a newspaper printed in 1946. The mass-specific emission rate from the four paper samples in our study are within the same range. The mass-specific emission rate of formic acid and acetic acid ranged from 262 ng g! h'! from the book printed in 1993 (sample no. 3) up to 1692 ng g! h! from the newspaper printed in 2017 (sample no. 4). the newspaper printed in 2017 (sample no. 4).

Table 3. Concentration of organic acids (sum of formic acid and acetic acid) in one storage building with mechanical ventilation (1), two rooms in another storage building with semi-passive climate control (II) and outdoor. The measurements were conducted in winter and summer. Table 3 shows the concentration of organic acids (sum of formic acid and acetic acid) outdoor and inside Storage I and the two rooms in Storage II in winter and summer. The concentration outdoor was below the LOQ in winter and summer. The concentration of formic acid and acetic acid were larger inside the storage buildings than outdoor. It is assumed that internal sources as the heritage collections themselves contribute to the concentrations of formic acid and acetic acid inside the storage buildings as the storage rooms contain non- emissive construction materials and building interior such as concrete and metal that would not contribute significantly to the concentrations of formic acid and acetic acid.

Table 4. Temperature (monthly average) in all three storage rooms in winter and summer. 3 in both rooms. Within the same period the temperature increased 7-8°C whereas RH variations remained within the uncertainty of the sensor (43% RH). A study by Krupinska et al. [19] showed a similar trend where the concentration of formic acid and acetic acid increased 5-6 times from winter to summer, and Smedemark and Ryhl-Svendsen [20] showed an 3-8 times increase in the concentration of formic acid and acetic acid with a 7°C increase in temperature from winter to summer within three storage buildings with archival and library collections in Denmark. Our study demonstrated how the emission rates of formic acid and acetic acid as well as the concentration in air inside real storage buildings with heritage collections depend on the temperature. as the concentration in air inside real storage buildings with heritage collections depend on the temperature.

_ Table 5 shows 36 VOCs detected as emissions during chamber tests from the four paper samples (no. 1-4). The recycled newspaper printed in 2017 emitted the largest number of VOCs. Almost all VOCs detected from the paper samples were measured in trace concentrations below 10 pg m® (shown in light blue in Table 5). Identified substances released by the four paper samples detected in chamber air correspond with the VOC profile from paper made of rag and ground-wood pulp found in previous studies [1, 3, 6-7, 27-31]. Compounds as toluene, ethylhexanol, nonanal and decanal were detected as emission substances from all four samples. Gibson et al. [1] detected the same compounds as emission substances from books.

Figure 21 – uploaded by Signe Hjerrild Smedemark

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