Abstract: A filter for removing contaminants from a gas contains a support material and, deposited on the support material, a first component which is an oxide, a hydroxide or a mixture of an oxide and hydroxide of Al, Si, Ti, Fe or Zn, containing at least about 0.5% by weight of water. The first component is deposited onto the filter preferably from a colloidal sol solution of a compound of the metal of that component. The first component acts as an adsorbent to remove contaminants from a gas, such as air. The filter may contain a second component, such as an alkali metal, alkaline earth metal, permanganate(s), or a mixture thereof. The filter may also contain a third component, such as an adsorbent, in the form of separate particles, e.g., activated charcoal, potassium permanganate, activated alumina, optionally treated with an alkali metal or alkaline earth metal compound(s), zeolites, and alumino-silicate compositions.