Backpack sprayers are one of the most widely known types of hand-held sprayers for spraying pesticides. They are widely used in a wide range of crops in tropical countries and are also called backpack or lever sprayers. The earliest knapsack sprayer had a brass water tank. The basic sprayer components of the canister, side rod, pump and pressure chamber, the spray gun with on-off control and at least one nozzle are easily identifiable on modern devices.

However, many significant advances have been made in the materials used in the manufacture of sprayers, and manufacturers have also produced variants of some components, such as pump types or tank volumes, pressure controllers and nozzles. There are now a variety of knapsack sprayers to choose from, with different component types and functions provided by different manufacturers.

Knapsack sprayers are usually chosen because their purchase cost is usually relatively low, operation and maintenance are simple, and they are easy to carry. They are particularly useful for spraying pesticides in areas where large mechanized sprayers cannot operate due to restricted access, inappropriate ground conditions, or obstacles such as tall vegetation.

To ensure the safe use of backpack sprayers, it is essential to understand this and other causes of potential exposure and take all practical measures to limit any potential exposure of the operator to pesticides. Ensuring that the appropriate applicator is selected and operating normally, with no leaks or potentially harmful contamination, will help minimize the possibility of operators being contaminated by pesticide solutions and ensure that they maintain control over their operations.