A total of twenty-three (23) firms with a total of forty-six (46) teams are accredited to carry out the stack testing for PM, CO, NOx as NO2 and SOX as SO2 pursuant to DAO 2013-26. The TPSETF undergoes written, oral and proficiency exam in order to pass the accreditation. These are done by the Sampling Assessment Team (SAT) which are selected personnel of AQMS from the central and regional offices. The said team also conducts regular monitoring/observation of accredited firms to ensure that they continuously follow proper testing procedure. Annual training on stack emission testing are also carried out in order to provide lectures to stack testers aside from the regular coordination meeting to discuss updates, issues and concerns.