Bangladesh has a tropical monsoon climate with a five month period of very heavy rain and maximum summer temperatures up to 36.5 degrees C. Relative humidity is especially high from June through September. These conditions present a challenge to conservators, as most reactions that lead to decay of materials increase in rate with temperature and humidity. Without air conditioning, indoor temperature and humidity fluctuate with outdoor conditions. The National Museum is air conditioned, but only during hours when the museum is open. Storage rooms are equipped with dehumidifiers during the season of very high humidity, and air is allowed to circulate at other times. Exhibition cases are made of wood and other hygroscopic materials, and generally present more stable conditions. Another major problem is dust, which may be a breeding ground for fungus and bacteria. Sweeping with a mop helps keep the dust down. Intense light exposure is avoided, since it may bleach colors and lead to other forms of deterioration. Regular inspections of gallery areas is used to monitor all these conditions. Finally, the severe limitations on funding mean that museum construction should be planned carefully with conservation needs in mind.