Typically, the spec is 10 ng/Nm3 (0.01 µg/Nm3) for natural gas upstream of cryogenic units.
For sales gas (pipeline), it can vary from 10 ng/Nm3 to 20-30 µg/Nm3, typically 1-5 µg/Nm3 but depends on the buyer.
For naphtha, LPG and ethane, the spec is typically around 1-5 wt ppb, depending on what the product is used for.
To reach this specification, solid adsorbents can be used. Metal sulphide on alumina last longer.