Wildfire events can significantly increase indoor PM2.5 and VOCs, based on work by researchers at Washington State University. In a detailed analysis of air exchanges between indoor and ambient air, during and outside of wildfire events, researchers examined the indoor and outdoor concentrations of fine particles, ozone, and a number of VOCs in two test homes. Generally, indoor concentrations of particles were lower than outdoors, for the homes studied, but the effect of wildlfires was noticeable even in a fully closed home. PM penetration factors for these homes were 11% and 15%, with windows and doors closed. VOC levels were generally higher indoors and not associated with ambient concentrations, indicating indoor sources, although acetonitrile and benzene levels were elevated during wildfire episodes, due to introduction from ambient air. Penetration factors for ozone varied between 5% and 24% for the two homes