Pollutants can be classed as:

• Solid/particulate e.g. dust
• Gaseous e.g.
• Liquid

Particulate

People are the principle source of dust, through the clothing fibres, skin and hair they shed. They also bring in inorganic particulates on their clothes, as well as mud and grit on shoes, pushchairs, wheelchairs and equipment.

Air movement will bring in light particles including by products from industry such as fuel ash, salts, clay, sand and carbon based products from traffic.

Dust is also generated from the deterioration of the fabric of a building and its contents. More dust will be generated during periods of activity such as building works, filming and large events.

Damage

• Visual change : shiny surfaces appear dull, colours changed, texture obscured
• Mechanical damage: dust particles are sharp and will cause abrasive damage, sticky dirt will attract more dust and dirt. Removal of dust may in itself cause mechanical damage
• Biological damage: will sustain a microclimate of higher RH and supply food source therefore encouraging growth of mould and pests
• Chemical damage: dust is hygroscopic (will attract moisture) and therefore encourage chemical reactions such as rusting.

Monitoring

• Visual – regular inspections and agree level of presentation
• Scientific – various pieces of equipment are available which will measure dust deposition in a given time and space

Control

• Ensure windows and doors fit well and are not kept open unnecessarily
• Good door mats, scrapers at entrance to remove dust and dirt from visitors shoes as they enter the building
• If possible keep vulnerable objects on open display as far as possible from the visitors
• Ensure good routines of regular vacuuming and cleaning
• Protect vulnerable objects with case covers or display cases

Includes man made gases such as sulphur dioxide which are present in the air in higher concentrations than normal. Some are by products of industry and combustion, others produced by materials within the room.

Damage:

Pollutant	Source	Damage
Sulphur dioxide (Converts to more damaging sulphuric acid)	Fuel combustion	Embrittlement of paper Red rot on leather Weakening of textiles Rusting of metals As acid rain damages stone and plaster
Nitrogen oxide	Fuel combustion Gas heaters	Fading of pigments and dyes Weakening of textiles Breakdown of plastics Embrittlement of film and photographic materials
Ozone	Naturally present in air Combustion fumes in strong sunlight Photocopiers and laser printers	Fading of dyes and pigments Fading and embrittlement of photographic materials Cracking of rubber and plastics
Hydrogen sulphide	Degrading organic matter Wet wool Vulcanized rubber Some paints and sealants	Tarnishing silver Fading and yellowing of photographs
Volatile organic compounds	Organic or petroleum materials Given off during “off gassing” Most common are acetic acid, formic acid and formaldehyde Wood, fresh paint, sealants, textiles, MDF and degrading plastics	Corrosion of metals Damage to calcareous materials Damage to varnishes, lacquers, plastics, films and modern adhesives

Smell

• Can be a useful indicator of high concentrations , however some gases are harmful in levels too low for our noses to detect

Sampling

• Determines presence and concentration of specific gases
• Analytical devices are available which give a snapshot of gases present

Testing effects on materials

• Investigate the combined effects of gases in synergy with other environmental factors on test samples
• Metal coupons, egg shells and paint or plastic based dosimeters can all be used to detect the presence harmful gases

Avoidance

• Avoid introduction of any material that will off gas or allow to of gas before use

Exclusion

• Managing the building to reduce air exchange with outside
• Put vulnerable objects inside well sealed display cases or storage cases

Removal

• Use passive adsorption to remove pollutants e.g. plasters and cement, render, acid free packing material e.g. acid free tissue
• Use of pollution scavengers e.g. activated charcoal
• Ventilation and air circulation may help particularly in display cases with internally generated VOCs

• Liquid contaminants can be introduced as splashes, spills and leaks or carried in the air as tiny droplets in spray.
• Perspiration from handling or wearing clothes
• Preparing and consuming food and drink
• Aerosols e.g. air fresheners, artificial smells
• Building works or events
• Misguided care and using inappropriate cleaning products

Damage:

Acids and alkalis	May corrode metal and calcareous surfaces
Salts	Damage to copper alloys and iron
Solvents	Can cause dyes to run Dissolve glues Bloom in varnish Can result in complete dissolution May dry out organic material

Monitoring

• Vigilance and use of correct procedures

Control

• Manage food and drink preparation and consumption in location of vulnerable objects
• Use clean hands or gloves when handling certain objects
• Correct use of cleaning materials