Some humidors contain a permanent humidifying system which keeps the air moist, which in turn keeps the cigars moist. Without a humidor, within 2 to 3 days, cigars will quickly lose moisture and level up with the general humidity around them. The ideal relative humidity in a humidor is around 68–72%. Though it can vary slightly depending on the cigar smoker's preferences, it should never go higher than 75% due to the possibility of hatching tobacco beetles. The more empty space, the more readily the humidity level of the box will fluctuate.