Fire directly consumes cultural heritage through burning or deposition of smoke and soot on surfaces. Fire suppression systems can also cause damage, for example water damage from sprinklers. For example, around 18 million objects were destroyed in the 2018 fire at the National Museum of Brazil.

Preventive maintenance is essential to prevent and minimize the risk of fire. Strategies include prohibiting smoking and other sources of flames and heat; routine maintenance of fire extinguishers; maintaining a regular schedule for smoke detector maintenance and testing; and protecting the building and its contents with sprinkler systems.[5][6][7]​.

Materials can be classified according to their level of vulnerability to heat and combustion. Jean Tetrault identified five levels of sensitivity: from very low for non-combustible materials to very high for self-flammable and easily combustible materials. Inorganic materials, such as ceramics, stone, glass and metal, have a lower relative sensitivity to fire, compared to organic materials, such as wood, paper or textiles, which are highly reactive to fire.[8] Certain materials are known for their extremely high relative sensitivity to fire, such as organic solvents with a flash point below 32 C which makes them flammable and more dangerous if it drops below 21 C.[9]​.

An object's susceptibility to fire is a prominent factor that affects the speed at which fire can spread in space. Considering that fire is an exothermic chain reaction that produces energy in the form of light and heat, it is important to note that for the chain reaction to persist, the fuel must be in adequate conditions and quantity. If the material is wet, the heat produced will first react with the water to remove the moisture rather than directly causing the fuel to decompose and causing the chain reaction to continue if there is sufficient fuel source to feed on.[10]​.

Relative humidity (RH) can cause changes or damage to cultural heritage when the RH is too high, too low or when it fluctuates. High relative humidity can cause mold growth, salt disintegration, increased pest activity, wood swelling, rapid metal corrosion, and accelerated hydrolysis reactions in paper and other substrates. Low relative humidity can cause cracking and shrinkage of wooden objects, and drying and embrittlement of paper and organic textiles.[11] Fluctuations in relative humidity compound these effects and cause physical damage when organic materials contract and expand, particularly in mixed media objects where materials expand and contract at different rates (e.g., paintings on panels).[12] For this reason, museum environments often have humidity control as part of your heating, ventilation and cooling (HVAC) system, to keep relative humidity stable and within defined limits.[13]​.

Relative humidity is the amount of water contained in air expressed as a percentage of the total amount of water that could be contained in completely saturated air at a given temperature. The ability of air to retain moisture is directly related to temperature, as hot air can retain more water than cold air.

Some changes to objects are reversible by adjusting the relative humidity, but damage such as cracks can be irreversible. Keeping the RH within a range appropriate for the type of material and as consistent as possible will prevent most damage caused by RH. Maintaining storage and display spaces between 40 and 60% relative humidity will prevent most harmful effects, but maintaining stable relative humidity is often considered more important than meeting absolute ranges.[14] Professional conservation organizations such as the International Institute for Conservation (IIC), the International Council of Museums (ICOM-CC), the American Institute for Conservation (AIC), and the Australian Institute for the Conservation of Cultural Property (AICCM) have developed guidelines for museum environments.

The relative humidity of spaces can be measured using a variety of tools, including humidity indicator cards, thermohygrographs, hygrometers, psychrometers, and data loggers. HR data is monitored and analyzed to determine if adjustments are needed. Adjustments may be possible through humidifiers, dehumidifiers, adjustments to existing heating and air conditioning systems, and passive control measures.

Some objects have different HR needs than others on your display or in your warehouse. For those items, you need to create special cases or storage containers to meet your needs. In them, the RH and temperature may be different from those present in the rooms. Some special boxes and containers can also be made to ensure the safe travel of objects.[15]​.

Two primary mechanisms of chemical deterioration affecting cultural heritage include hydrolysis and oxidation, which can result in chain scission or cross-linking. These occur at room temperature to varying degrees (depending on the material); The rate of chemical reactions increases with temperature. Consequently, cold storage (e.g., storage at 10°C, 4°C, or below zero) is often used to slow the deterioration of vulnerable materials such as cellulose nitrate and cellulose acetate film.

Higher temperatures can also cause softening or melting of materials with low melting points, such as waxes and some plastics. Some materials become brittle and temperatures drop, increasing the chance of physical damage during handling. When frozen, ice crystals can physically alter delicate surfaces such as photographic emulsions.

Light, as it relates to collection maintenance, is primarily concerned with the visual and ultraviolet (UV) light ranges of the electromagnetic spectrum. Exposure to visible light will fade many dyes. Higher energy wavelengths of ultraviolet light can also cause discoloration, yellowing, and physical weakening of substrates, causing some materials to become brittle and prone to breaking. Light radiation provides energy to induce chemical changes within the molecular structure of materials. Damage caused by light, including loss of color and strength, is cumulative and irreversible.[16]​.

Controlling light damage is a compromise process, as light is also necessary for people working with or viewing cultural heritage objects. Light exposure can be reduced by limiting the amount of time sensitive objects are displayed or the intensity with which they are illuminated. Dimmers, timers, and motion sensors can be used to limit exposure times.[17] Cultural organizations often develop schedules for display changes, in order to control the rate at which light-induced damage occurs. Light levels for light-sensitive objects, such as textiles, works on paper, and dyed leather, are generally kept at lower levels where possible (for example, at 50 lux), with 200 lux being a more common guideline for more light-resistant materials, such as oil paints, bones, and natural leather. Some types of materials, such as stone, metal, and glass, are not negatively affected by visible light.[18]​.

Ultraviolet light is not typically necessary for vision (unless UV-induced fluorescence is an important part of the viewing experience), so cultural organizations tend to eliminate or shield natural light sources from storage or display spaces. Shades, shades, and filters that absorb UV rays are also useful control strategies.[19]​.

Light and UV levels can be measured with an exposure meter so adjustments can be made.[20]​.

Many insect species feed on organic material from cultural heritage; For example, carpet beetles (some species of Attagenus and Anthrenus) and clothes moths are attracted to protein-based fibers such as wool and silk; silverfish graze on the surface of books and photographs; Several species of borers can infest wooden furniture or frames. Insects can be attracted to the accumulation of dust and debris on objects to feed on them. Insects, birds and rodents may use cultural heritage objects as nesting material, soil them with droppings, or damage them by scratching and piercing them. Bird poop can etch the surface of an outdoor metal sculpture, and birds' feet can scratch its surface.

Damage caused by insects and other museum pests often occurs because these pests are attracted to objects in collections that they view as a food source. Certain types of materials, such as wood, organic textiles, furs, and paper, are more vulnerable to insect damage than others.[21]​.

Integrated pest management or IPM has become a key strategy in monitoring and controlling pests in museum environments. IPM focuses on prevention, through cleaning and maintenance, and monitoring pest populations through the use of a sticky trap system. This allows museum or repository staff to identify vulnerable locations, detect new infestations, and identify the type of insects present and then act to eliminate the infestation.[21]​.

There are a variety of possible treatments available to address insect infestations. Insecticides are no longer the preferred treatment method for cultural objects due to risks to human safety and often undesirable effects on the objects themselves.[21]​ Instead, non-chemical methods are preferred, including freezing, controlled heating, radiation, and hypoxic treatments.[21]​ Even options as simple as regulating the temperature and relative humidity of a space can be effective in reducing an infestation, depending on the pest.[21]​ Each option has advantages and disadvantages. drawbacks, and the choice of the treatment used should be made in consultation with a qualified professional.[21]​.

Air pollutants such as ozone, sulfur dioxide, hydrogen sulfide, and nitrogen dioxide cause corrosion, acidification, and discoloration of a variety of materials. Indoor contaminants such as formaldehyde and other volatile organic acids cause similar problems and may be present in carpets, paints and varnishes or in the materials used to construct display cases or storage furniture (wood, plastics, fabrics, resins). Objects can also generate contaminants internally; For example, deterioration of cellulose acetate film results in the generation of acetic acid, which can damage other nearby objects.

Air pollutants can tarnish or corrode metal objects. Silver objects are vulnerable to sulfur gases that tarnish them, and lead and pewter objects corrode when exposed to volatile organic acids.[22] Damage can be minimized by storing vulnerable silver objects in enclosures with activated carbon or in silver-plated tea, which absorbs sulfur.[23] Silver objects can also be coated or lacquered with a transparent barrier material such as Paraloid B-72 thermoplastic to prevent corrosion. tarnish, but these coatings require periodic reapplication. A potential source of volatile organic acids is wooden shelves or wooden storage and display furniture.[24]​.

Dust is also classified in this context as an exterior and interior contaminant, as it can damage the surface by abrasion when removed or stain it by absorbing moisture. Dust may contain skin, mold, and inorganic fragments such as silica (Silicon(IV) oxide") or sulfur. Dust can become stuck to a surface over time, making it much more difficult to remove.[25] Dust is also hygroscopic, meaning it is able to attract and retain water molecules, creating an ideal climate for mold spores to grow and cause biological damage.[26] The hygroscopic nature of dust can also cause chemical reactions on a surface, especially on metals. Inorganic dust particles can have sharp, tough edges that can tear fibers and abrade softer surfaces if not properly removed.

Dust accumulation can be prevented by storing and displaying collectibles in closed cabinets or boxes, or by using dust covers. Dust minimization strategies also include the use of air filters in heating and air conditioning systems, the use of vacuum cleaners equipped with HEPA filters, and cleaning strategies with soft cloths.[19]​[26]​.

Physical forces include sources of mechanical damage, where objects can bend, break, distort, wear, etc. The change is caused by some applied force, which can be as varied as seismic motion from earthquakes, road vibration, electrical equipment, amplified music, or by simple storage accidents such as bumps and scrapes, or handling accidents in which objects are hit or knocked over.

Training and handling guidelines help prevent accidental damage due to physical forces when moving and working with museum objects. Handling guidelines may contain tips for carefully inspecting objects before picking them up, clearing the path of obstacles and tripping hazards, lining carts and trolleys for transport with polyethylene foam padding, and planning all steps of a procedure in advance.[27]​ In storage, objects are housed so that they are easily accessible,[28]​ and fragile objects may have custom holders or supports and padded storage boxes.

This category, sometimes called "criminals", includes theft or deliberate damage to cultural heritage. There are many famous examples, such as the theft of paintings from the Isabella Stewart Gardner Museum in 1990, or the 2012 attack on the Rothko painting at the Tate Gallery,[29]​ although many thefts may go unreported or even go unnoticed in large institutions, or where inventory checks are infrequent.

Control strategies include limiting access to collections based on their value, rarity, portability and/or accessibility, both for staff and potential visitors. Storage and display furniture may be locked and alarmed. Cultural organizations can install security cameras, motion sensors and alarms and employ security guards and patrols.[30]​[5]​.

Water damage typically occurs from leaks in the building structure or from flooding associated with weather events or failures of water transport infrastructure (plumbing, wet pipe sprinkler systems, air conditioning).

Condensation "Condensation (change of state)") can occur when the air temperature suddenly drops, such as when warm indoor air hits a colder external wall or window. Water can soften or solubilize applied media (paints, adhesives, coatings), cause staining and leaving marks after evaporation, cause physical damage upon impact, weaken substrates and encourage the growth of microorganisms, and swell, shrink or distort organic materials. Water can also carry pollutants and pollutants, such as sludge and sewage, which leave stains. The Florence flood of 1966 was a formative moment in the development of the conservation-restoration profession and, in particular, preventive conservation.

This is not the only conceptual framework used to categorize material deterioration in the cultural heritage professions. For example, deterioration can also be classified according to its source: biological, chemical and physical.[31]​.

The ten agents of deterioration are often used as a framework for sustainability debates in the cultural heritage sector, when the cost of controlling or minimizing deterioration is weighed against the perceived benefits. Costs can be financial (for example, the cost of running air conditioning), environmental (for example, the use of plastics as storage and packaging material, or the use of solvents for conservation treatments, or the use of energy to run air conditioning systems), or even the labor necessary to sustain an activity. The impacts of established conservation and restoration practices on the environment and climate change are increasingly debated, particularly the profession's emphasis on strict control of temperature and humidity.

Recent environmental guidelines for cultural heritage collections, such as those developed by the Australian Institute for the Conservation of Cultural Materials (AICCM),[32] emphasize sustainability and resilience as a guiding principle and make direct reference to climate change as a reason for frequent review. These guidelines highlight the need to consider the local climate and allow for variations in relative humidity and temperature values ​​accordingly.

Fire directly consumes cultural heritage through burning or deposition of smoke and soot on surfaces. Fire suppression systems can also cause damage, for example water damage from sprinklers. For example, around 18 million objects were destroyed in the 2018 fire at the National Museum of Brazil.

Preventive maintenance is essential to prevent and minimize the risk of fire. Strategies include prohibiting smoking and other sources of flames and heat; routine maintenance of fire extinguishers; maintaining a regular schedule for smoke detector maintenance and testing; and protecting the building and its contents with sprinkler systems.[5][6][7]​.

Materials can be classified according to their level of vulnerability to heat and combustion. Jean Tetrault identified five levels of sensitivity: from very low for non-combustible materials to very high for self-flammable and easily combustible materials. Inorganic materials, such as ceramics, stone, glass and metal, have a lower relative sensitivity to fire, compared to organic materials, such as wood, paper or textiles, which are highly reactive to fire.[8] Certain materials are known for their extremely high relative sensitivity to fire, such as organic solvents with a flash point below 32 C which makes them flammable and more dangerous if it drops below 21 C.[9]​.

An object's susceptibility to fire is a prominent factor that affects the speed at which fire can spread in space. Considering that fire is an exothermic chain reaction that produces energy in the form of light and heat, it is important to note that for the chain reaction to persist, the fuel must be in adequate conditions and quantity. If the material is wet, the heat produced will first react with the water to remove the moisture rather than directly causing the fuel to decompose and causing the chain reaction to continue if there is sufficient fuel source to feed on.[10]​.

Relative humidity (RH) can cause changes or damage to cultural heritage when the RH is too high, too low or when it fluctuates. High relative humidity can cause mold growth, salt disintegration, increased pest activity, wood swelling, rapid metal corrosion, and accelerated hydrolysis reactions in paper and other substrates. Low relative humidity can cause cracking and shrinkage of wooden objects, and drying and embrittlement of paper and organic textiles.[11] Fluctuations in relative humidity compound these effects and cause physical damage when organic materials contract and expand, particularly in mixed media objects where materials expand and contract at different rates (e.g., paintings on panels).[12] For this reason, museum environments often have humidity control as part of your heating, ventilation and cooling (HVAC) system, to keep relative humidity stable and within defined limits.[13]​.

Relative humidity is the amount of water contained in air expressed as a percentage of the total amount of water that could be contained in completely saturated air at a given temperature. The ability of air to retain moisture is directly related to temperature, as hot air can retain more water than cold air.

Some changes to objects are reversible by adjusting the relative humidity, but damage such as cracks can be irreversible. Keeping the RH within a range appropriate for the type of material and as consistent as possible will prevent most damage caused by RH. Maintaining storage and display spaces between 40 and 60% relative humidity will prevent most harmful effects, but maintaining stable relative humidity is often considered more important than meeting absolute ranges.[14] Professional conservation organizations such as the International Institute for Conservation (IIC), the International Council of Museums (ICOM-CC), the American Institute for Conservation (AIC), and the Australian Institute for the Conservation of Cultural Property (AICCM) have developed guidelines for museum environments.

The relative humidity of spaces can be measured using a variety of tools, including humidity indicator cards, thermohygrographs, hygrometers, psychrometers, and data loggers. HR data is monitored and analyzed to determine if adjustments are needed. Adjustments may be possible through humidifiers, dehumidifiers, adjustments to existing heating and air conditioning systems, and passive control measures.

Some objects have different HR needs than others on your display or in your warehouse. For those items, you need to create special cases or storage containers to meet your needs. In them, the RH and temperature may be different from those present in the rooms. Some special boxes and containers can also be made to ensure the safe travel of objects.[15]​.

Two primary mechanisms of chemical deterioration affecting cultural heritage include hydrolysis and oxidation, which can result in chain scission or cross-linking. These occur at room temperature to varying degrees (depending on the material); The rate of chemical reactions increases with temperature. Consequently, cold storage (e.g., storage at 10°C, 4°C, or below zero) is often used to slow the deterioration of vulnerable materials such as cellulose nitrate and cellulose acetate film.

Higher temperatures can also cause softening or melting of materials with low melting points, such as waxes and some plastics. Some materials become brittle and temperatures drop, increasing the chance of physical damage during handling. When frozen, ice crystals can physically alter delicate surfaces such as photographic emulsions.

Light, as it relates to collection maintenance, is primarily concerned with the visual and ultraviolet (UV) light ranges of the electromagnetic spectrum. Exposure to visible light will fade many dyes. Higher energy wavelengths of ultraviolet light can also cause discoloration, yellowing, and physical weakening of substrates, causing some materials to become brittle and prone to breaking. Light radiation provides energy to induce chemical changes within the molecular structure of materials. Damage caused by light, including loss of color and strength, is cumulative and irreversible.[16]​.

Controlling light damage is a compromise process, as light is also necessary for people working with or viewing cultural heritage objects. Light exposure can be reduced by limiting the amount of time sensitive objects are displayed or the intensity with which they are illuminated. Dimmers, timers, and motion sensors can be used to limit exposure times.[17] Cultural organizations often develop schedules for display changes, in order to control the rate at which light-induced damage occurs. Light levels for light-sensitive objects, such as textiles, works on paper, and dyed leather, are generally kept at lower levels where possible (for example, at 50 lux), with 200 lux being a more common guideline for more light-resistant materials, such as oil paints, bones, and natural leather. Some types of materials, such as stone, metal, and glass, are not negatively affected by visible light.[18]​.

Ultraviolet light is not typically necessary for vision (unless UV-induced fluorescence is an important part of the viewing experience), so cultural organizations tend to eliminate or shield natural light sources from storage or display spaces. Shades, shades, and filters that absorb UV rays are also useful control strategies.[19]​.

Light and UV levels can be measured with an exposure meter so adjustments can be made.[20]​.

Many insect species feed on organic material from cultural heritage; For example, carpet beetles (some species of Attagenus and Anthrenus) and clothes moths are attracted to protein-based fibers such as wool and silk; silverfish graze on the surface of books and photographs; Several species of borers can infest wooden furniture or frames. Insects can be attracted to the accumulation of dust and debris on objects to feed on them. Insects, birds and rodents may use cultural heritage objects as nesting material, soil them with droppings, or damage them by scratching and piercing them. Bird poop can etch the surface of an outdoor metal sculpture, and birds' feet can scratch its surface.

Damage caused by insects and other museum pests often occurs because these pests are attracted to objects in collections that they view as a food source. Certain types of materials, such as wood, organic textiles, furs, and paper, are more vulnerable to insect damage than others.[21]​.

Integrated pest management or IPM has become a key strategy in monitoring and controlling pests in museum environments. IPM focuses on prevention, through cleaning and maintenance, and monitoring pest populations through the use of a sticky trap system. This allows museum or repository staff to identify vulnerable locations, detect new infestations, and identify the type of insects present and then act to eliminate the infestation.[21]​.

There are a variety of possible treatments available to address insect infestations. Insecticides are no longer the preferred treatment method for cultural objects due to risks to human safety and often undesirable effects on the objects themselves.[21]​ Instead, non-chemical methods are preferred, including freezing, controlled heating, radiation, and hypoxic treatments.[21]​ Even options as simple as regulating the temperature and relative humidity of a space can be effective in reducing an infestation, depending on the pest.[21]​ Each option has advantages and disadvantages. drawbacks, and the choice of the treatment used should be made in consultation with a qualified professional.[21]​.

Air pollutants such as ozone, sulfur dioxide, hydrogen sulfide, and nitrogen dioxide cause corrosion, acidification, and discoloration of a variety of materials. Indoor contaminants such as formaldehyde and other volatile organic acids cause similar problems and may be present in carpets, paints and varnishes or in the materials used to construct display cases or storage furniture (wood, plastics, fabrics, resins). Objects can also generate contaminants internally; For example, deterioration of cellulose acetate film results in the generation of acetic acid, which can damage other nearby objects.

Air pollutants can tarnish or corrode metal objects. Silver objects are vulnerable to sulfur gases that tarnish them, and lead and pewter objects corrode when exposed to volatile organic acids.[22] Damage can be minimized by storing vulnerable silver objects in enclosures with activated carbon or in silver-plated tea, which absorbs sulfur.[23] Silver objects can also be coated or lacquered with a transparent barrier material such as Paraloid B-72 thermoplastic to prevent corrosion. tarnish, but these coatings require periodic reapplication. A potential source of volatile organic acids is wooden shelves or wooden storage and display furniture.[24]​.

Dust is also classified in this context as an exterior and interior contaminant, as it can damage the surface by abrasion when removed or stain it by absorbing moisture. Dust may contain skin, mold, and inorganic fragments such as silica (Silicon(IV) oxide") or sulfur. Dust can become stuck to a surface over time, making it much more difficult to remove.[25] Dust is also hygroscopic, meaning it is able to attract and retain water molecules, creating an ideal climate for mold spores to grow and cause biological damage.[26] The hygroscopic nature of dust can also cause chemical reactions on a surface, especially on metals. Inorganic dust particles can have sharp, tough edges that can tear fibers and abrade softer surfaces if not properly removed.

Dust accumulation can be prevented by storing and displaying collectibles in closed cabinets or boxes, or by using dust covers. Dust minimization strategies also include the use of air filters in heating and air conditioning systems, the use of vacuum cleaners equipped with HEPA filters, and cleaning strategies with soft cloths.[19]​[26]​.

Physical forces include sources of mechanical damage, where objects can bend, break, distort, wear, etc. The change is caused by some applied force, which can be as varied as seismic motion from earthquakes, road vibration, electrical equipment, amplified music, or by simple storage accidents such as bumps and scrapes, or handling accidents in which objects are hit or knocked over.

Training and handling guidelines help prevent accidental damage due to physical forces when moving and working with museum objects. Handling guidelines may contain tips for carefully inspecting objects before picking them up, clearing the path of obstacles and tripping hazards, lining carts and trolleys for transport with polyethylene foam padding, and planning all steps of a procedure in advance.[27]​ In storage, objects are housed so that they are easily accessible,[28]​ and fragile objects may have custom holders or supports and padded storage boxes.

This category, sometimes called "criminals", includes theft or deliberate damage to cultural heritage. There are many famous examples, such as the theft of paintings from the Isabella Stewart Gardner Museum in 1990, or the 2012 attack on the Rothko painting at the Tate Gallery,[29]​ although many thefts may go unreported or even go unnoticed in large institutions, or where inventory checks are infrequent.

Control strategies include limiting access to collections based on their value, rarity, portability and/or accessibility, both for staff and potential visitors. Storage and display furniture may be locked and alarmed. Cultural organizations can install security cameras, motion sensors and alarms and employ security guards and patrols.[30]​[5]​.

Water damage typically occurs from leaks in the building structure or from flooding associated with weather events or failures of water transport infrastructure (plumbing, wet pipe sprinkler systems, air conditioning).

Condensation "Condensation (change of state)") can occur when the air temperature suddenly drops, such as when warm indoor air hits a colder external wall or window. Water can soften or solubilize applied media (paints, adhesives, coatings), cause staining and leaving marks after evaporation, cause physical damage upon impact, weaken substrates and encourage the growth of microorganisms, and swell, shrink or distort organic materials. Water can also carry pollutants and pollutants, such as sludge and sewage, which leave stains. The Florence flood of 1966 was a formative moment in the development of the conservation-restoration profession and, in particular, preventive conservation.

This is not the only conceptual framework used to categorize material deterioration in the cultural heritage professions. For example, deterioration can also be classified according to its source: biological, chemical and physical.[31]​.

The ten agents of deterioration are often used as a framework for sustainability debates in the cultural heritage sector, when the cost of controlling or minimizing deterioration is weighed against the perceived benefits. Costs can be financial (for example, the cost of running air conditioning), environmental (for example, the use of plastics as storage and packaging material, or the use of solvents for conservation treatments, or the use of energy to run air conditioning systems), or even the labor necessary to sustain an activity. The impacts of established conservation and restoration practices on the environment and climate change are increasingly debated, particularly the profession's emphasis on strict control of temperature and humidity.

Recent environmental guidelines for cultural heritage collections, such as those developed by the Australian Institute for the Conservation of Cultural Materials (AICCM),[32] emphasize sustainability and resilience as a guiding principle and make direct reference to climate change as a reason for frequent review. These guidelines highlight the need to consider the local climate and allow for variations in relative humidity and temperature values ​​accordingly.