Pollutants and Collections


If you are familiar with the 10 Agents of Deterioration, you know that pollutants can cause damage to collections. In this context, pollutants are the chemicals that deteriorate or accelerate deterioration of collection objects. Pollutants can be generated outside and migrate into collections spaces (nitrogen oxide compounds from vehicle exhaust), but they can also be generated inside collections spaces (aldehydes generated by wood furniture). In some cases, collections, themselves can be the source of a pollutant that damages objects around them (nitric acid produced by cellulose nitrate based film). Damage caused by pollutants can include physical soiling in addition to chemical changes like the tarnishing of metals, the fading of dyes, the weakening of cellulose, or the formation of crystalline compounds or droplets on the surface of objects.  

Collection pollutants may differ from pollutants in a human health and safety context. For some collections, sodium chloride, oxygen, and water are pollutants. Common collection pollutants, their sources, and affected materials are summarized in Table 1. 

Table 1: Summary of common collection pollutants adapted from Tétreault 2021  


Collections Affected 

Common Indoor Sources 


Metals, cellulose nitrate, ebonite 

Concrete; certain sealants, adhesives, and paints; some cleaning products; humans 

Acetic acid 

Metals, paper, shell specimens, stone, soda-rich glass, paper-based objects 

Cellulose acetate; certain sealants, adhesives, and paints; linoleum; some cleaning products; humans 


Metals, some artists’ colorants, stone, ceramic, shell specimens, glass, paper-based objects 

Composite wood products like fiberboard; solid wood; wet specimens  

Nitrogen oxide compounds 

Metals, paper-based objects, leather, some artists’ colorants, photographs 

Cellulose nitrate; gas heaters 

Sulfur dioxide 

Metals, paper, leather, some artists’ colorants 

Degradation of sulfur-containing materials: proteinaceous fibers, sulfide minerals, vulcanized rubber 


Some artists’ colorants, paper-based objects, rubber, dyes, digital prints 

Photocopiers; laser printers; ultraviolet light sources; electronic air cleaners; electrostatic filtered systems 

Hydrogen sulfide 

Metals, photographs, lead pigments 

Sulfide minerals; visitors; fuel and coal combustion; plastic degradation; vulcanized rubber 


All, especially magnetic media, metals, natural varnishes 

Concrete; laser printers; construction; humans; cooking and food; burning candles; coal combustion; aerosol humidifiers 


The risk of pollutant damage increases in microenvironments (like sealed cases) because pollutants cannot escape, elevating their concentrations. This can be damaging to human health and safety in the case of pollutant-producing collections. For example, ventilated storage is recommended for collections made of malignant plastics such as cellulose nitrate.  


There is currently no pollutant equivalent to a temperature/relative humidity datalogger that can be read in house within the budgets of many collecting institutions. A relative humidity monitor actually is a pollutant monitoring device, but it only monitors for a single pollutant: water vapor. Because there are so many different pollutants and there are so many different components of air, it is, at this stage, impossible to have one monitoring device that can accurately measure all the pollutants collections stewards are worried about. Institutions must “pick their battles.” Are you most concerned about a specific collection? Are you worried about the potential that a new material has for off-gassing? Do you have the resources to pursue implementing a monitoring system that is expensive and extensive? 

There are a wide range of pollutant monitoring techniques that vary in their accessibility, specificity, and ability to produce quantitative results. Some examples are presented in Table 2. 

Table 2: Sample of pollutant monitoring techniques 

Type of Technique 





Screen for pollutants that are damaging to a specific collection material. 

Placing metal coupons among collections to indicate if the environment is corrosive. 

Does not identify or quantify pollutants. 


Measure concentrations of specific pollutants or families of pollutants. 

Placing ozone badges among collections to measure ozone exposure. 

Careful attention must be paid to interferences and detection limits. 


Identify and quantify multiple pollutants. 

Running air samples through gas chromatograph to separate and measure components. 

Not all pollutants detected. For example, detecting hydrogen sulfide using GC requires specialized set-up. 


Techniques of varying costs and detection limits are outlined in the 2006 book by Cecily Grzywacz, Monitoring for Gaseous Pollutants in Museum Environments, and Jean Tétreault’s 2021 technical leaflet, “Control of Pollutants in Museums and Archives – Technical Bulletin 37”.  

While it is preferable that pollutants be intercepted before damage occurs, monitoring sensitive collections can also be informative. Deterioration of these sensitive materials can be an indicator that a specific pollutant is present. Table 3 lists examples of sensitive materials and the pollutants that commonly affect them.  

Table 3: Examples of hypersensitive materials and corresponding pollutants. Adapted from Tétreault 2003, 2021 



Pollutants Indicated 

Cellulose acetate 

Vinegar smell, embrittlement, film shrinkage 

Acetic acid (self-produced), water vapor 

Cellulose nitrate 

Yellowing, sticky residue, image fading 

Nitrogen oxides (self-produced), water vapor 



Acetic acid 

Natural rubber 

Embrittlement, cracking; spongey, sticky   

Ozone, oxygen 

Fine silver 


Hydrogen sulfide 

Polyurethane magnetic tape 

Sticky shed syndrome 

Water vapor, particles 


Particulates can be monitored directly because they are visible. Simple dust collectors made with tape and label stock or paper can provide a baseline for dust accumulation that informs housekeeping policies and allows later comparison following mitigation activities. 


Mitigation depends on the pollutant and the form it takes, but a general rule of thumb for pollutant mitigation is to avoid, block, dilute, filter, or sorb pollutants in that order. Figure 1 shows examples of mitigation strategies that fall within those five categories. 

Some collection materials also adsorb and desorb pollutants. This increases the importance of keeping temperature and relative humidity stable to minimize spikes in pollutant levels. 

If you have further questions or concerns about potential monitoring and mitigation options for pollutants in your institution, consult a professional conservator. The “Find a Professional” database of the American Institute for Conservation can help you identify a professional who has expertise with the type of collections under review. https://community.culturalheritage.org/expertsearch 

Additional Resources 

Brimblecombe, Peter. “Air Quality, Monitoring, and Management,” in Elkin, Lisa and Christopher Norris, eds. Preventive Conservation: Collection Storage. New York: Society for the Preservation of Natural History Collections, 2019.  

Gryzwacz, Cecily M. Monitoring for Gaseous Pollutants in Museum Environments. Los Angeles: Getty Publications, 2006.   https://www.getty.edu/conservation/publications_resources/pdf_publications/monitoring_gaseous.html

Hatchfield, Pamela. Pollutants in the Museum Environment. London: Archetype Publications, 2002. 

Hatchfield, Pamela. “Pollutants in the Museum Environement: Practical Strategies for Problem Solving in Design, Exhibition, and Storage.” WAAC Newsletter, vol. 26, no. 2, May 2004, pp. 10–22. https://cool.culturalheritage.org/waac/wn/wn26/wn26-2/wn26-204.pdf 

Tetreault, Jean. Airborne Pollutants in Museums, Galleries, and Archives. Ottawa: Canadian Conservation Institute, 2003. 

Tétreault, Jean. Control of Pollutants in Museums and Archives: Technical Bulletin 37. CCI Technical Bulletin, Canadian Conservation Institute, 2021. https://www.canada.ca/en/conservation-institute/services/conservation-preservation-publications/technical-bulletins/pollutants-museums-archives.html#a13. 

Weintraub, Steven. “Specialized Macroclimates and Microclimates: Options for the Control of Temperature, Relative Humidity, and Pollutants,” in Elkin, Lisa and Christopher Norris, eds. Preventive Conservation: Collection Storage. New York: Society for the Preservation of Natural History Collections, 2019.  

Williams, R. Scott. “Care of Plastics: Malignant Plastics.” WAAC Newsletter 24(1), 2002. https://cool.culturalheritage.org/waac/wn/wn24/wn24-1/wn24-102.html 

Updated July 2022.