Handheld machines, manual machines or portable machines are "Machine (technology)" machines that allow the work of traditional hand tools to be mechanized. Hand-held machines are equipped with a drive mechanism that replaces or complements the human force that was the only one used in classic hand tools. In the 19th century, handheld machines began to be equipped with electric motors, which increased their ease of use. Apart from these, they are also available with pneumatic drives or powered by a combustion engine. Handheld machines can produce large amounts of particles, including ultrafine particles, airborne particles that are a group 1 carcinogen.

The hand-held machine is closely related to the machine tool due to the type of work that both types allow to perform. The essential difference is that a machine tool is fixed, and is mounted on a fixed frame or on a table, while a hand-held machine is portable and can be transported from one place to another easily, with your hands. In practice, both concepts sometimes overlap since some handheld machines can be mounted on a fixed support as in the case of the drill stand.

Although hand-held power tools are useful, they also produce large amounts of noise, vibration[1]​ and particles, including ultrafine particles.[2]​ Airborne particles are a group 1 carcinogen.[3]​ atmospheric[4]​ as they can penetrate deep into the lungs and brain from the bloodstream, causing health problems such as heart disease, lung disease and premature death. [5]​ There is no safe level of particles. lung cancer in Europe." [6]​ Worldwide, exposure to PM 2.5 contributed to 4.1 million deaths from heart disease, stroke, lung cancer, chronic lung diseases and respiratory infections in 2016. [7]​ Overall, the parts from premature to [8]​ .

There are some industry standards for the size and amount of dust emitted by power tools, [9]​ [10]​ although they do not appear to be widely known or used globally. Knowing that dust is generated throughout the construction process and can cause serious health risks, [11] manufacturers now market power tools equipped with dust collectors (e.g., HEPA vacuum cleaners) or integrated water supply systems that extract dust after emission. [12]​ [13]​ However, the use of these products is still not common in most places. Starting in the first quarter of 2024, gasoline tools are prohibited in California. [14]​.