4. The Scottish Ministers shall, in particular, consider measuring the following volatile organic compounds–
| Ethane | 1-Butene | Isoprene | Ethyl benzene |
| Ethylene | trans-2-Butene | n-Hexane | m+p-Xylene |
| Acetylene | cis-2-Butene | i-Hexane | o-Xylene |
| Propane | 1.3-Butadiene | n-Heptane | 1,2,4-Trimeth. benzene |
| Propene | n-Pentane | n-Octane | 1,2,3-Trimeth. benzene |
| n-Butane | i-Pentane | i-Octane | 1,3,5-Trimeth. benzene |
| i-Butane | 1-Pentene | Benzene | Formaldehyde |
| 2-Pentene | Toluene | Total non-methane hydrocarbons |