A system and method for ensuring non-interfering garbage collection in a real time multi-threaded environment. The method comprises strengthening silicon penetration devices by thermally growing a silicon oxide layer on the penetration device and then subsequently stripping the silicon oxide. Coasting is only enabled if, for a specified minimum number of successive travel points, the evaluation result is in each case positive. The method further includes maintaining the reactant batch at a temperature between about 70\xb0 Fahrenheit and 180\xb0 Fahrenheit. The microwave oven includes an air cleaning button formed on a control panel of the microwave oven, a controller for determining an input signal from the air cleaning button and generating a driving signal, and a fan driving part for operating a fan disposed in the microwave oven to allow intake air to pass through a filter, thereby removing pollutants contained in the intake air. In one aspect, the method includes using spacers with respective radial spokes which connect inner and outer portions of the case.