UD7 MÉTODO COSHH ESSENTIALS
Analysis of Technical Note 936: The COS Method
Overview of the COS Method
- The COS method allows for qualitative assessment of occupational exposure to chemical agents without specific measurement tools. This is regulated by norms that permit reliable evaluation methods.
- Originating from Britain, COS stands for "Control of Substances Hazardous to Health," focusing on evaluating processes involving chemical contaminants and preventive measures.
Risk Assessment Variables
- Risk levels range from 1 to 4 based on the hazard level, quantity used, and volatility or dustiness of the chemical agent. These are determined using a specific table.
- Hazard categories are classified as A, B, C, D, and E; with E being the most dangerous. Categories are derived from H phrases (or R phrases in older regulations) associated with each chemical agent.
Understanding Chemical Properties
- For example, formaldehyde has an H351 phrase indicating potential cancer risk, categorizing it as D due to its danger level. If multiple phrases exist, the highest danger category is selected.
- Volatility is assessed based on boiling points; liquids have low/medium/high volatility depending on their boiling point relative to working temperatures (e.g., formaldehyde at ambient temperature shows medium volatility). Solid contaminants require knowledge of their dustiness levels (low/medium/high).
Quantity Assessment
- Quantity classifications include small (grams/milliliters), medium (kilograms/liters), and large (tons/cubic meters). Each classification impacts overall risk assessment outcomes.
Linking Variables to Risk Levels
- Once hazard level, quantity, and volatility/dustiness are established, one can determine the corresponding potential risk level using a predefined table (e.g., hazard C with medium quantity and low volatility results in potential risk level 2). Notably, any hazard rated E automatically corresponds to a potential risk level 4.
Control Measures Associated with Risk Levels
- Different control measures correspond to each risk level:
- Level 1: General ventilation required.
- Level 2: Localized extraction system needed.
- Level 3: System must be closed.
- Level 4: Quantitative evaluation with measurements necessary.
Special Considerations for Carcinogens
- Specific legislation applies for carcinogenic or mutagenic compounds; quantitative evaluations must be conducted whenever a potential risk level of 4 is identified. Modifications in hazard categories may occur based on daily exposure limits or LoAEL values outlined in technical notes.
Application Example of COS Method
Process Description
- An example involves manufacturing DISA through mixing reactant liquid React1 with caustic soda at a concentration of 40%. The final compound consists of only 1% React1 mixed predominantly with caustic soda across four stages requiring individual assessments for hazards and quantities involved in each stage.
Stage Assessments:
- Stage One: Emptying bags of sodium hydroxide categorized as C due to R35 phrase; characterized by low dustiness and medium quantity handling.
- Stage Two: Dissolving sodium hydroxide in water retains category C status due to R35 phrase; also exhibits low volatility since it's a solid dissolved in water while maintaining medium quantity handling.
- Stage Three: Adding Reactant liquid indicates medium volatility based on its boiling point at high temperatures while managing less than one liter classifies it as small quantity.
- Final Stage: The resulting mixture containing both React1 and sodium hydroxide inherits category D due to its composition including React1 which poses higher risks despite being only at a concentration of 1%.