The national framework regulation on hazardous substances (GefStoffV) 1

The Ordinance on Hazardous Substances, which came into force at the beginning of 2005 and in a new version in 2010, implements several EC directives and regulates occupational safety in activities involving hazardous substances. The Hazardous Substances Ordinance applies to welding fumes, for example, as welding fumes are classified as hazardous substances by the Technical Rules for Hazardous Substances (TRGS) 528.

The welding fume particles are inhalable and respirable; in the case of chromium-nickel steels, they are carcinogenic. The Hazardous Substances Ordinance 1 requires local extraction: "Dust must be collected as completely as possible at the point of emission or origin and disposed of without risk. The extracted air must be conducted in such a way that as little dust as possible gets into the breathing air of the employees. The extracted air may only be returned to the work area if it has been sufficiently cleaned. It further states: "Equipment for separating, collecting and precipitating dust must be state-of-the-art. When these devices are put into operation for the first time, their sufficient effectiveness must be checked. At least once a year the equipment must be checked for proper functioning, maintained and, if necessary, repaired. The recorded results of the tests according to sentences 2 and 3 shall be kept. (Annex I No.2, § 2.3, Paragraph 5 and Paragraph 7)

Air recirculation when handling carcinogenic substances

"If activities involving carcinogenic, mutagenic or fertility-endangering hazardous substances of categories 1 and 2 are carried out in a work area, the air extracted there must not be returned to the work area. This does not apply if the air is sufficiently purified of such substances by using procedures or equipment recognized by the authorities or by the institutions of the statutory accident insurance. The air must then be conducted or cleaned in such a way that carcinogenic, mutagenic or fertility endangering substances do not enter the breathing air of other employees. (§ 10 GefStoffV, paragraph 5)

If the welding fumes contain carcinogenic components - such as nickel compounds or chromates - the exhaust air must be discharged into the atmosphere. In exceptional cases, the clean air can be recirculated. In this case, the requirements of TRGS 560 3 "Technical Rules for Hazardous Substances - Air recirculation for activities involving carcinogenic, mutagenic and fertility-endangering dusts" must be met.

Tips for users
To meet the regulations, both mobile dust extractors and central stationary systems are available to the operator. IFA-tested (formerly BGIA) dust collectors (according to the internationally valid standard DIN EN ISO 15012-1) and centralized systems according to TRGS 528 comply with the legal requirements

Extract from TRGS 528 2
4.5 Air recirculation: (1) Exhausted air may only be recirculated into the working area if it is sufficiently cleaned. Ventilation systems with recirculation
may be used if they are type-tested or if the required effectiveness has been verified by individual measurements. BGR 121 "Workplace Ventilation - Ventilation Measures" contains information on the fresh air content of ventilation systems with air recirculation.

(2) At workplaces where welding work or related processes with emissions of carcinogenic, mutagenic or fertility hazardous substances of category 1 or 2 are performed (in particular, if materials containing chromium and nickel are used), air exhausted from the workplace shall not be recirculated. This shall not apply if type-tested welding fume extraction units of welding fume separation class W2 or W3 are used. For information on the welding fume separation classes, see DIN EN ISO 15012-1 "Occupational health and safety in welding and allied processes - Requirements, testing and marking of air cleaning systems - Part 1 Determination of the separation efficiency of welding fumes" of March 2005.

(from TRGS 528 of February 2009)