established concentrations which, if not exceeded, will not generally cause adverse effects to the worker exposed. Exposure limits differ in name and meaning depending on origin. For example: 1. The exposure levels for the hazardous chemicals that are included in the Regulation respecting the Control of Exposure to Biological or Chemical Agents - made under the Occupational Health and Safety Act of Ontario, are expressed as follows: TWAEV Time-Weighted Average Exposure Value: the average airborne concentration of a biological or chemical agent to which a worker may be exposed in a work day or a work week. | STEV Short Term Exposure Value: the maximum airborne concentration of a chemical or biological agent to which a worker may be exposed in any 15 minute period, provided the TWAEV is not exceeded. | CEV Ceiling Exposure Value: the maximum airborne concentration of a biological or chemical agent to which a worker may be exposed at any time. | SKIN: this notation indicates that direct or airborne contact with the product may result in significant absorption of the product through the skin, mucous membranes or eyes. Inclusion of this notation is intended to suggest that preventative action be taken against absorption of the agent through these routes of entry. | 2. Threshold Limit Values (TLVs) are exposure guidelines developed by the American Conference of Governmental Industrial Hygienists (ACGIH). They have been adopted by several Canadian governments and others as their legal limits. They are expressed as follows: TLV - TWA Threshold Limit Value - Time-Weighted Average: the time-weighted average concentration for a normal 8 hour work day and a 40 hour work week, to which nearly all workers may be repeatedly exposed, day after day, without adverse effect. | TLV - STEL Threshold Limit Value - Short Term Exposure Limit: a 15 minute time-weighted average exposure which should not be exceeded at any time during a work day even if the 8 hour TWA is within the TLV. Exposures at the STEL should not be repeated more than 4 times a day and there should be at least 60 minutes between successive exposures at the STEL. | TLV - C Threshold Limit Value - Ceiling: the concentration that should not be exceeded during any part of the working exposure. Other exposure limits include the Permissible Exposure Limits (PEL) which are legal exposure limits in the United States. | Fines: Finely crushed or powdered material or fibres; especially those smaller than average in a mix of various sizes. | Flammable Limits: See "Explosive Limits". | Flammable Substance: one that will readily catch fire and continue to burn in air if exposed to a source of ignition. | 1.Flammable Aerosol: a material that is packed in an aerosol container which can release a flammable material. | Flammable Gas: a gas which can readily catch fire and continue to burn. | 2. Flammable Gas: a gas which can readily catch fire and continue to burn. | 3.Flammable Liquid: a material that gives off a vapour which can readily catch fire and continue to burn. A flammable liquid has a flashpoint below 37.8oC. | 4. Flammable Solid: a material which can readily catch fire and continue to burn vigorously and persistently. This may occur from friction, absorbing moisture, from spontaneous chemical change, or by retaining heat from manufacturing or processing. 5. Reactive Flammable Material: a material which is a dangerous fire risk because it can react readily with air or water.