Products and spraying
VOC released on a job and VOC content as applied
- where
- total VOC released (g)
- VOC content of the paint (g/L)
- paint used (L)
- VOC content of the thinner, 0 for water (g/L)
- thinner added (L)
- VOC content of the mix as applied (g/L)
- headroom below the legal limit (g/L)
- legal limit for the product category (g/L)
Explain this equation
Adds up the solvent (volatile organic compounds) a job releases and checks the paint as applied against the legal limit for its category. Useful for COSHH assessments and when thinning solvent-borne paint.
c is the VOC content printed on the tin or data sheet and V the litres used. ct and Vt are the same for any thinner: zero for water, about 780 g/L for white spirit, which is almost entirely volatile. m is the total mass of VOC, cr the content of the ready-to-use mix, and Llim the limit for the product category.
Each liquid contributes its VOC content times its volume. Dividing the total by the total volume gives the concentration of the mix, which is what the 2012 Regulations limit. The headroom is the limit minus that figure.
Sense check: 20 litres of a 10 g/L masonry paint release just 200 g of VOC. Adding half a litre of white spirit to 5 litres of a 290 g/L trim paint adds 390 g and takes the mix to about 335 g/L, over the 300 g/L limit.
Watch out: this is not a room exposure level; ventilation and the safety data sheet decide that.
Adds up the solvent (VOC) a job releases into the room and checks the ready-to-use mix against the legal limit for its category.
Enter your values to see the result.
Good to know
The VOC Regulations 2012 cap VOC in ready-to-use decorative paint, for example 30 g/L for interior matt walls and ceilings (category a), 40 g/L for water-borne exterior masonry paint (c), 130 g/L water-borne and 300 g/L solvent-borne trim paint (d). The tin and data sheet state the category limit and the product's maximum. White spirit is essentially all volatile, so its VOC content is about its density, roughly 780 g/L. HSE advises substituting water-based products, ventilating, and using vapour-filter RPE where needed; record it in your COSHH assessment.
Common mistake
Thinning a compliant solvent-borne paint with white spirit beyond the data sheet's allowance, which can push the mix over the limit and greatly increases the vapour in a small room.
Limits
Assumes volumes add and all VOC is released. Does not give an exposure level in the room: that depends on room volume and ventilation, so follow the COSHH assessment and the safety data sheet.
Sources
- The Volatile Organic Compounds in Paints, Varnishes and Vehicle Refinishing Products Regulations 2012 (SI 2012/1715), Schedule 2 Table A: maximum VOC g/L of ready-to-use product
- NetRegs: Solvent limits in paints and varnishes
- HSE: Construction hazardous substances – Solvents (substitute water-based products, ventilate, correct vapour-filter RPE, COSHH assess–control–review)
- Painting and Decorating Association: COSHH assessments for painting and decorating businesses (templates for emulsion and white spirit use)
- Tikkurila Lakkabensiini 1050 (white spirit) product data sheet: density 0.78 kg/L (ISO 2811)
- Dulux Trade Weathershield Smooth Masonry Paint data sheet (volume solids 38% white; do not apply below 7 °C or above 80% RH; recoat 2–4 h; VOC max 10 g/L against 40 g/L limit, cat. A/c; airless thinning up to 1 part water to 5 parts paint)
Results are calculations from the published methods and figures shown, and depend on the data you enter. Coverage depends on the product, surface and application. Always follow the paint and wallcovering manufacturers’ data sheets and BS 6150 / BS 8000-12. Check prices and VAT with your own records and HMRC.