Dust presents a physical risk to objects and reduces evidential value; it also creates a perception of poor standards of care. However, cleaning also imposes risks of damage, takes time and costs money. The presence of visitors induces much of the dust found in properties, so increasing or extending access has implications for housekeeping that are rarely discussed in economic terms, despite the fact that dust control represents the most expensive element of preventive conservation in historic houses. The range of preventive and protective measures that minimize the deposition of dust also carry costs that often relate to visitor flow. Simple economic calculations show the balance between the costs of cleaning and of other equipment and materials in National Trust properties. The cost per visitor initially reduces with increased numbers of people, but at high flow rates expenditure can increase because of the cost of cleaning. The per capita conservation costs become less than UK?2 per visitor at reasonable visitor flow rates (about 30000 per annum), although, in the calculations presented here for an idealized medium-sized property, costs begin to increase as visitor flow rises above 60000 per annum. Recognizing the economic importance of managing dust is thus essential in assessing the level of access consistent with maintaining appropriate standards of presentation and collections care.