PQS stands for Performance, Quality and Safety. Under it, WHO publishes specifications and test procedures for equipment used in immunisation programmes and lists products that have been assessed against them. Categories cover cold chain equipment such as refrigerators and freezers, which are grouped under category E003, as well as cold boxes, vaccine carriers, temperature monitoring devices and other items.
Prequalified products have been tested for things that matter in the field, such as temperature performance at high ambient temperatures, hold-over time, freeze protection and durability. Many national programmes and procurement agencies buy immunisation cold chain equipment from the PQS list. Listings carry validity dates and are updated, so buyers should check the current WHO catalogue rather than rely on an old document.
When a state health department in India procures ice-lined refrigerators for new health centres, its specifications typically refer to WHO PQS-listed models and the national programme's guidelines.