Ultrafine particles are smaller than 0.1 microns, make up about 90% of all airborne particles and have been linked to heart attacks, strokes, asthma, respiratory conditions, and even cancer. IQAir HyperHEPA filtration in the GC and GCX Series filters 95% of all particles down to 0.003 microns – the smallest particles that exist, including airborne viruses and bacteria.