Hi,
As far as my knowledge is concerned, it has not been mentioned directly in the OHSAS Std. that we should follow national and international std. for PPEs but If you refer clause 4.3.2 (Legal and other requirements) it clearly indicates that we have to comply our local legal requirement.
I also would like to suggest you please refer factory acts book of your state.
Please keep into mind that The purpose of personal protective equipment (PPE) is to protect individuals during exposure to any hazard
Here, I am giving you the example of Eye/face PPEs
All Eye/Face Protection – Equipments designed to provide protection to the face and eyes during exposure to such hazards as flying particles, molten metal or sparks, liquid chemicals, acids or caustic liquids, or potentially injurious light radiation - so thickness of PPEs is most important as per the Standards.