Pure Grignard reagents are extremely reactive solids. Higher than normal concentrations of oxygen lead to increased levels of reactive oxygen species. Aldehydes are highly reactive and participate in many reactions. Ozone is a highly toxic and extremely reactive gas. The reaction proceeds via the formation of a highly reactive "O"-acylisourea. This action catalyzes production of reactive radicals and reactive oxygen species. There are several behavioral responses common towards stressors including the proactive, reactive, and passive responses. Glycols and polyols are highly reactive toward KMnO. Metallic sodium is generally less reactive than potassium and more reactive than lithium. This is known as the chemical part of reactive ion etching. Hazardous waste may be toxic, ignitable, corrosive, reactive, or radioactive. Historically, silver had the advantage over other metals of being less chemically reactive. Such anisotropy is maximized in deep reactive ion etching. This principle relies on substances harmful to humans being usually more reactive than air. Silica analysis in UPW typically includes determination of reactive and total silica.