Modifiers matching impurity:

• anionic,
• harmless,
• corrosive,
• airborne,
• physical,
• fine,
• damaging,
• initial,
• foreign,
• heavier,
• microscopic,
• gaseous,
• common,
• coarse,
• volatile,
• insoluble,
• small,
• fluid,
• stubborn,
• chemical,
• hazardous,
• soluble,
• mechanical,
• up,
• reactive,
• unwanted,
• desirable,
• sticky,
• out,
• light,
• ionic,
• suspended,
• organic,
• atmospheric,
• visible,
• nonpolar,
• ordinary,
• lighter,
• active,
• separate,
• harmful,
• lightweight,
• unavoidable,
• undesired,
• minor,
• off,
• polar,
• mental,
• particulate,
• dissolved,
• inorganic,
• minute,
• random,
• heterogeneous,
• mobile,
• little,
• dilute,
• natural,
• residual,
• colloidal,
• solid,
• environmental,
• interfering,
• biological,
• micro,
• smaller,
• absorptive,
• possible,
• homogeneous,

Simple categories matching gaseous:

• hydrocarbon,
• waste,
• olefin,
• fuel,
• mass,
• form,
• molecule,
• fluid,
• salt,
• substance,
• substrate,
• cyanide,
• atmosphere,
• compound,
• body,
• contaminant,
• matter,
• anesthetic,
• component,
• buffer,
• pollutant,
• carrier,
• impurity,
• fumigant,
• acid,
• chemical,
• agent,
• anaesthetic,
• object,
• oxide,
• material,
• medium,
• alkyne,
• sulphide,
• phenomenon,
• precursor,
• alkane,
• contamination,
• plasma,
• system,
• odor,
• mixture,
• monomer,
• reactant,
• constituent,
• state,
• flow,