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GB 50325 is a mandatory standard issued by the Chinese Ministry of Construction. It is mainly used for on-site examination of air pollution caused by materials used in civilian building projects and interior decoration. The standard can also be applied to pollution control of construction and decoration processes.

What’s involved in GB 50325?

In this method, BTX and TVOCs are determined using tube-based thermal desorption.

Appendix D of GB 50325 defines the sampling and analytical method for indoor benzene, toluene and xylene. Coconut charcoal or Tenax TA–Carbograph X sorbents are specified to trap these compounds.

Appendix E of GB 50325 describes measurement of indoor TVOC. 16 VOCs are listed, with volatilities ranging from hexane to hexadecane. Any unrecognised peaks are measured as peak-area toluene equivalents, and the TVOC concentration is then calculated by summing these values. Tenax TA or Tenax–Carbograph X sorbents are specified to trap these compounds.

Complying with GB 50325

Problems such as background interference, carryover and poor reproducibility are often encountered during use of this method.

However, Markes’ TD100-xr and UNITY–ULTRA-xr, together with DiffLok technology, can eliminate these issues. In addition, overlap mode can greatly improve sample throughput.