Case Study: Indoor Air Quality Assessment at a Historic Book Archive

Sysco Environmental Ltd was engaged to conduct an indoor air quality assessment at a historic library building located in Leeds. This three-storey period structure in the city centre features a basement used for book storage and upper floors serving as public areas. The assessment was initiated in response to long-standing issues with dampness and mould growth affecting the book collections in the basement.
 
The library is a historic institution with a rich heritage dating back to its establishment in the 18th century. As one of the oldest subscription libraries in the United Kingdom, it has played a significant role in the intellectual and cultural development of Leeds and its surrounding areas. The building itself is a period town structure with robust construction, ensuring durability and security for its valuable collections.
 
The library boasts an extensive and diverse collection of books, spanning various genres and historical periods. This includes rare manuscripts, early printed books, and unique editions of great significance to scholars, historians, and bibliophiles. Over the centuries, a treasure trove of literary works, including notable first editions, classical literature, and significant academic texts, has been assembled here.
 
Preserving these invaluable collections has always been a priority. The building management has faced challenges related to environmental conditions, such as dampness and mould growth, which can severely damage books and manuscripts. To combat these issues, the basement storage areas have been equipped with advanced air-conditioning and dehumidification systems. These measures are crucial in maintaining optimal humidity levels and preventing the ingress of water, which could otherwise lead to deterioration of the book materials.

Methodology for Indoor Air Quality Assessment at a Library

 
The air quality survey at the library was designed to identify and quantify airborne fungal spores and evaluate surface contamination in the basement book storage areas. The comprehensive methodology included spore trap sampling, culturable methods, and moisture mapping to build a detailed picture of the prevailing environmental conditions.
 

 Airborne Spore Trap Sampling

 
To assess the airborne mould spore concentrations, we used Vesta Spore Trap cassettes. These devices are effective in capturing a wide range of fungal spores and particulates from the air. The sampling process involved using High Flow 1600 air sampling pumps, calibrated both before and after sampling to ensure accuracy. Each sample was collected over a ten-minute period, with a total volume of 200-250 litres of air passed through the spore trap. This method is crucial for understanding the airborne exposure risks to library staff and visitors.
 

 Culturable Methods for Viable Mould Sampling

 
Viable mould samples were collected using SKC biostage samplers. These samplers were equipped with microbiological growth plates containing Malt Extract Agar (MEA) or Sabouraud Dextrose Agar (SDA) media, conducive to the growth of a broad spectrum of mould species. The sampling flow rates were carefully calibrated to maintain consistency and reliability. After collection, the samples were incubated and analysed to identify the viable mould species present. This culturable method provides insight into the specific types of moulds and their potential health risks.

 Surface Sampling

 
Surface sampling was conducted to determine the extent and nature of fungal colonisations on various surfaces within the basement, particularly the book storage areas. Swab samples and contact plates were used to collect specimens from visible mould colonies. The analysis of these samples helps identify specific mould species and their growth patterns, often influenced by localised moisture conditions.
 

Moisture Mapping

 
Moisture levels were mapped using the Hydromette HB30 and Tramex Moisture Encounter Plus moisture meters. These instruments detect moisture content within building materials, critical for understanding the conditions that support mould growth. By mapping moisture levels across different areas of the basement, we could correlate high moisture zones with areas of mould colonisation.
 

 Building a Comprehensive Environmental Picture From Air Sampling Data

 
The combination of airborne spore trap sampling, viable mould culturable methods, and detailed moisture mapping provides a robust framework for assessing workplace air quality. By identifying the specific mould species and their associated moisture requirements, we can infer the prevailing environmental conditions within the basement. This information is critical for developing targeted interventions to manage mould growth and protect the rare book collections stored in the basement.
 
The methodology employed by Sysco Environmental Ltd in the indoor air quality survey of the library is thorough and multifaceted, aimed at understanding and mitigating the risks posed by fungal spores. By integrating spore trap sampling, culturable methods, and moisture mapping, we provide comprehensive insights into the environmental conditions and airborne exposure risks, ensuring the preservation of the library's valuable book collections and the health of its occupants.

Findings and Conclusion of Our Indoor Air Quality Survey

 
The indoor air quality assessment at the library revealed significant insights into the fungal contamination levels within the basement book storage areas. The comprehensive sampling and analysis allowed us to quantify the airborne exposure risks and identify specific areas of concern.
 
- Airborne Spore Concentrations: The results indicated that the indoor air quality in the basement was significantly affected by fungal spores, particularly of the Aspergillus/Penicillium type. The spore trap samples collected in the basement showed concentrations ranging from 178 to 54,017 counts per cubic meter (cts/m³). The background concentration of fungal spores outside the building was measured at 3,298 cts/m³. For example, Book Store 1 East had 2,101 cts/m³, a 36% decrease from the background, indicating some areas with lower contamination levels. In contrast, Book Store 4 Centre showed a significantly higher concentration at 54,017 cts/m³, a 1,538% increase over the background, indicating a severe contamination hotspot.
- Dominant Fungal Species: Qualitatively, the samples were dominated by Aspergillus/Penicillium spores, which made up over 90% of the spore count in some areas. For instance, in Book Store 4 Centre, Aspergillus/Penicillium spores accounted for 100% of the spore count, reflecting a significant indoor source of these moulds.
 
- Surface Contamination: Surface samples revealed the presence of Aspergillus brasiliensis on the surfaces of books in multiple book storage areas. This species, while not considered clinically significant, indicates active mould growth within the indoor environment. Collected samples consistently showed the presence of Aspergillus brasiliensis, correlating with the high airborne spore concentrations in these areas. The visible fungal contamination was classified as medium, with less than 10m² affected. This indicates a localised issue that, while not widespread, poses a significant risk due to the high spore concentrations in specific areas.
 
- Viable Fungal Spores: Viable fungal spore samples were also collected to assess the presence of living moulds capable of growing under suitable conditions. The concentration of viable fungal spores indoors was similar to the outdoor background levels, ranging from 118 to 1,240 colony-forming units per cubic meter (CFU/m³). For instance, Book Store 1 West had 663 CFU/m³, a 55% decrease compared to the background, while Book Store 6 Centre had 6,923 cts/m³, indicating elevated levels and the presence of an active indoor source. The viable spore samples confirmed the dominance of Aspergillus species, with Aspergillus brasiliensis being the most commonly identified. This consistent finding across multiple sampling methods reinforces the conclusion that the indoor environment is contributing to the fungal contamination.
 
The indoor air quality survey in the library basement revealed that the indoor environment is significantly impacted by fungal spores, particularly Aspergillus/Penicillium types. The airborne spore concentrations were notably higher than the external environment in certain areas, indicating active indoor sources of contamination. The presence of Aspergillus brasiliensis on surfaces and in viable spore samples further supports the conclusion of ongoing mould growth within the basement.
 
The elevated levels of airborne spores, particularly in hotspots like Book Store 4 Centre, pose a medium to high health risk to individuals working in these areas. The findings underscore the importance of enhancing ventilation, implementing moisture control measures, and using appropriate personal protective equipment (PPE) to mitigate exposure risks. By addressing these environmental conditions and maintaining rigorous monitoring, the library can safeguard its valuable book collections and ensure a healthier environment for its staff and visitors.

 Recommendations Based on Findings of Air Quality Monitoring

 
Based on the assessment, the following recommendations were made to address the fungal contamination and improve indoor air quality at the library basement:
 

1. Ventilation Improvements:

   - Importance: Increasing the ventilation rate in the basement is critical for aiding the drying process, decreasing humidity levels, and providing a constant supply of fresh air. Proper ventilation helps to remove excess moisture from the air, which is a key factor in preventing mould growth.
   - Implementation: Install or upgrade mechanical ventilation systems to ensure a continuous exchange of air. This will help maintain stable environmental conditions that are unfavourable for microbial growth. The system should be capable of regulating humidity levels, particularly during the winter months when the building is sealed.
 

2. Respiratory Protection:

   - Importance: The use of FFP3 standard respiratory protection is essential when working in the basement for extended periods. This type of protection filters out a high percentage of airborne particles, including fungal spores, reducing the risk of respiratory exposure.
   - Implementation: Ensure that all personnel working in the basement are equipped with FFP3 masks. Training on the correct use and maintenance of these masks should be provided to ensure their effectiveness.
 

3. Health Precautions:

   - Importance: Individuals with pre-existing respiratory illnesses, respiratory allergies, or compromised immune systems are at higher risk from exposure to fungal spores. Avoiding work in the basement can prevent exacerbation of these conditions.
   - Implementation: Develop and enforce health policies that restrict at-risk individuals from working in the basement. Offer alternative tasks or remote work options to these employees.
 

4. Fungal Control:

   - Importance: Regular monitoring and maintenance are crucial for controlling fungal growth and maintaining indoor air quality. Stable environmental conditions with very low humidity levels are necessary
 
 to prevent microbial decay of sensitive materials, such as rare books.
   - Implementation: Establish a routine inspection and cleaning schedule to identify and address any signs of mould promptly. Use dehumidifiers to maintain relative humidity levels below 50%, as high humidity creates ideal conditions for fungal growth. Regularly check and calibrate air conditioning and dehumidification systems to ensure optimal performance.
 

 Our Conclusion From the Air Quality Survey

 
The indoor air quality survey at the library highlighted the need for improved ventilation and stringent health precautions to manage the identified mould issues. By implementing these recommendations, the library can maintain stable environmental conditions and ensure a safer environment for staff and visitors.
 
Maintaining very low humidity levels is particularly important to prevent microbial decay of sensitive materials, such as the library's rare book collections. Microbial attack occurs because cellulose, the primary component of paper, is an ideal food source for environmental fungi. By controlling humidity and ensuring proper ventilation, the library can significantly reduce the risk of fungal growth, thereby preserving the integrity of its valuable collections and protecting the health of its occupants.
 
By addressing these recommendations, the library can ensure a safer environment for staff and visitors while preserving its valuable book collections.