Advice on this can be found in the Building Research Establishment (BRE) / Environment Agency report BR 414 ‘Protective measures for housing on gas-contaminated land.
Gellir dod o hyd i gyngor ynghylch y mater hwn yn adroddiad y Sefydliad Ymchwil Adeiladu / Asiantaeth yr Amgylchedd - BR414 'Protective measures for housing on gas-contaminated land.