In general, liquid spray devices or atomizers can be categorized into two types: pneumatic and manual pump. Pneumatic atomizers utilize a pressurized carrier gas to disperse a flowable liquid as small aerosolized particles, and are commonly used in cosmetics and pharmaceuticals. Examples of pneumatic atomizers include dispensers of fragrances, antiperspirants, and insecticides.
The advantage of using a pneumatic atomizer is that it can be made portable, often small enough to be carried in a pocket or purse. However, pneumatic atomizers are usually not refillable, costly to make, and can cost environmental problems if not disposed properly.
On the other hand, a manual pump type of atomizer dispenses liquid from its reservoir when the dispensing head or handle of the pump is pressed, sometimes repeatedly, to force the liquid content from the reservoir into a capillary tube and out of the dispensing orifice in either a mist or liquid form. This type of atomizer is typically made larger in size than the pneumatic type. Examples include dispensers of cleaning solutions, bath or shower gels, and moisturizing lotions.
Although the content of a manual-pump atomizer can sometimes be refilled, a problem often arises when the content volume is low and the atomizer is operated in a horizontal orientation or at an angle to the upright orientation. When the capillary conduit cannot reach the liquid content, the content cannot be dispensed. As such, it is almost impossible to dispense the content of a manual-pump atomizer in an upside-down orientation.