A cyclonic portable vacuum cleaner/dust collector has a cyclonic chamber and a filter chamber. The filter chamber contains a filter cartridge with a hollow core positioned over the discharge opening of a motor plate that closes the filter chamber. A vacuum blower is mounted on the motor plate, with an intake tube at the discharge opening of the motor plate. An anti-deflagration screen mounted upon the discharge opening of the cover plate of the filter chamber. The anti-deflagration screen is in the form of a metal mesh creating a multiplicity of small passages to permit exhaust air flow from the filter chamber but blocking any flame front. The screen may be hemispherically domed.