Nyob rau xyoo tas los no, kev txhim kho ntawm kev lag luam PVC tau nkag mus rau hauv qhov sib npaug tsis muaj zog ntawm kev muab khoom thiab kev thov. Tuam Tshoj lub voj voog kev lag luam PVC tuaj yeem faib ua peb theem. 1.2008-2013 Lub sijhawm loj hlob sai ntawm kev lag luam muaj peev xwm tsim khoom. 2.2014-2016 lub sijhawm rho tawm peev xwm tsim khoom2014-2016 lub sijhawm rho tawm peev xwm tsim khoom 3.2017 txog rau lub sijhawm sib npaug tam sim no, qhov sib npaug tsis muaj zog ntawm kev muab khoom thiab kev thov.
