What are WEL/OEL limits

WELs (Workplace Exposure Limits) are occupational exposure limits (OELs) which are set to help protect the health of workers, but, they are not levels above which harm will definitely arise and they are NOT levels below which harm will not arise. WEL's/OEL's do not address safety issues such as flammable concentrations. They are the measurement of concentrations of hazardous substances in the air, averaged over a specified time referred to as a time-weighted average (TWA).

There are two time periods used a long term, over an 8 hour reference period, and a short term, over a 15 minute period. The short term (STELs) are set to help prevent effects, such as eye irritation, which could occur after a few minutes.

UN transport codes

These codes are from the “ UN Model Regulations on the Transport of Dangerous Goods ”, they are not obligatory or legally binding on individual countries, but they have a wide degree of international acceptance and form the basis of several national laws and international agreements.
They include a classification system for substances that pose a significant hazard in transportation by air, sea, rail and inland waterways. The hazards addressed include explosive, flammability, toxicity (oral, dermal and inhalation), corrosive to human tissue and metal, reactivity, radioactivity, infectious substance hazards and environmental hazards. The regulations give standards for the packaging and for any tanks that are used for transport, they also layout a system of communicating the hazards of substances using pling and marking of packages, signage on tanks, freight containers and vehicles, and the documentation and emergency response information that is required to accompany each shipment.