Free tool
Emissions calculator
for your spray booth
How much dust and how much solvent is in the exhaust air? Enter the paint, area, film thickness and air volumes. The calculator shows the concentration in mg/m³ – and whether the limit values are met.
Energy
What does your exhaust air cost?
Every cubic metre of exhaust air has to be replaced by heated supply air and moved by fans. The calculator takes the air volumes of the spray booth, flash-off booth and oven from above and shows the cost per year – with and without heat recovery.
Method
How the calculator works.
A simple mass balance based on the guidance notes to the German TA Luft. Every step is disclosed.
1. Amount of paint
Dry film = area × film thickness × density
Paint without losses = dry film ÷ solids
Paint sprayed = paint without losses ÷ transfer efficiency
Solvents = paint sprayed × (1 − solids)
1 m² × 1 µm × 1 g/cm³ gives exactly 1 g. The rest is simple proportion.
2. Dust
Dust = paint sprayed × solids
× (1 − transfer efficiency)
× (1 − filter efficiency)
÷ (spray booth exhaust air × time*)
Only the overspray reaches the filter. Whatever the filter does not retain is spread over the exhaust air.
3. Solvents in the spray and flash-off booths
Spray booth = solvents × share spray booth × C factor
÷ (spray booth exhaust air × time*)
Flash-off booth = solvents × share flash-off booth × C factor
÷ (flash-off booth exhaust air × time*)
Most of the solvent evaporates in the spray and flash-off booths. The C factor (generally 0.67) converts solvents into carbon – because the limit values refer to total carbon.
4. Solvents in the dryer (oven)
Dryer = solvents × share dryer × C factor
÷ (dryer exhaust air × time*)
Little solvent, but little air as well. That is why the dryer and the flash-off booth are often more critical than the spray booth.
* Time = cycle time for an indexed line, time in the station for a batch.
Basis
- Guidance notes to the German TA Luft – use of solvents
- 31st BImSchV (German solvent ordinance), EU VOC Directive
- EN 12215 spray booths, EN 13355 combined spray and drying booths, EN 1539 dryers
- Common reference values: solid particles 3 mg/m³, organic substances 50 to 100 mg C/m³ (total carbon)
Indexed line or batch? On an indexed line, one part enters every station in each cycle. What counts is therefore the throughput per hour: the time in the formulas is the cycle time. A longer residence time in the oven does not dilute anything – it only determines how many parts hang in the oven at the same time. In a batch, all parts move together; there the solvents are spread over the time spent in each station.
Air costs: heating power per 1,000 m³/h = 1,000 × 1.2 kg/m³ × 1.005 kJ/(kg·K) ÷ 3,600 × temperature rise × (1 − heat recovery). The fans come on top. The air volume itself is determined by the booth technology and explosion protection – not by the limit value.
Please note: the calculator provides an estimate for planning purposes. It does not replace a measurement or an expert report. Which limit values apply to your plant depends on solvent consumption, the permit and the local authority. In Germany, manual plants below 25 kg/h are generally not subject to fixed requirements.
Values too high?
Let’s take a look together.
More air is rarely the best solution. A better transfer efficiency, a different filter or a material with less solvent often helps. I will work through the figures with you.