Filtering facepiece respirators Filtering facepiece respirator (FFPs) are disposable face masks produced from a whole piece of filtering material. FFPs (such as N95 masks) are discarded when they become unsuitable for further use due to considerations of hygiene, excessive resistance, or physical damage. Mass production of filtering facepieces started in 1956. The air was purified with nonwoven filtering material consisting of polymeric fibers carrying a strong electrostatic charge. Respirator was used in nuclear industry, and then in other branches of economy. For ~60 years, more than 6 billion respirators were manufactured. Unfortunately, the developers overestimated the efficiency (APF 200-1000 compared to the modern value of 10-20), which led to serious errors in the choice of personal protective equipment by employers. Elastomeric respirators A half-face elastomeric air-purifying respirator. This kind of respirator is reusable, with the filters being replaced periodically. Elastomeric respirators are reusable devices with exchangeable cartridge filters that offer comparable protection to N95 masks. The filters must be replaced when soiled, contaminated, or clogged. They may have exhalation valves. Full-face versions of elastomeric respirators seal better and protect the eyes. Fitting and inspection is essential to effectiveness. Powered air-purifying respirators (PAPRs) PAPRs are masks with an electricity-powered blower that blows air through a filter to the wearer. Because they create positive pressure, they need not be tightly-fitted. PAPRs typically do not filter exhaust from the wearer.
Mechanical filter 
Flow diverter
Articulatory technique
Vascular closure device
Pulmonary thrombectomy
Syringe filter
Thrombectomy
Pericardiectomy