Welding fume is made up of particulate fume and pollutant gases. The content of
the fume and its concentration will vary from one application to the next. Some
common components of fume are far more toxic than others and so present a much
greater potential to cause damage.
Measuring Particulate Welding Fume
In welding and cutting the particulate fumes consists mostly of:
- Metal oxides, from that parent material and consumables used.
- Organic materials caused by the breakdown of substances on the
surface of the material being welded such as paint or plastic
coatings.
- It must be remembered that there is often an interaction of
particulate and gaseous fume and this can affect the results
obtained.
Measurement Techniques
Measurement of particulate welding fume falls into two main
categories, personal sampling and bulk or laboratory sampling.
Personal sampling is carried out in the workplace
The principle of bulk sampling is to determine how much fume is
given off by a particular consumable or gas, in a set time at
known welding parameters. To take a breathing zone sample, the
filter holder is positioned alongside the cheek of the subject,
and if this is a welder, it must be positioned behind his
head-shield, if one is being used.
Units of Measurement
In personal sampling, the concentration of particulate fume and
each component of it are expressed in mg/m3 (milligrams per
cubic metre).
Bulk or Laboratory Sampling of Particulate Fume
Bulk samples of particulate fume are taken by consumable
manufacturers in their laboratories by means of an enclosed fume
box, often referred to as a 'Swedish Fume Box' due to its
country of origin.
The air and fume are drawn up through the box by some form of
suction device, normally a portable fume extraction unit.
Measuring Gaseous Welding Fume
In welding and cutting the gaseous fumes of most concern are:
- Oxides of Nitrogen
- Ozone (O3)
- Carbon Dioxide (CO2); Carbon Monoxide (CO)
- Organic Gases
Measurement Techniques
Measurement of gaseous welding fume falls into two main
categories, personal sampling and bulk or laboratory sampling.
Units of Measure
Gaseous fume is measured in ppm (parts per million) by means of
chemical reaction tubes or electronic equipment, in a
single-stage operation.
Personal Sampling of Gaseous Fume
The ready-calibrated detector tubes, about 100mm long, are
normally made of glass, and are filled with chemical reagents,
which undergo a colour change when exposed to a specific gas.
Each tube gives just one, instantaneous, reading and to obtain a
time-weighted average sample, several tubes must be used, one
after the other, over a known period of time.
Bulk or Laboratory Sampling of Gaseous Fume
The equipment required for the bulk analysis of gaseous fume
tends to be much larger than that required for particulate fume
because of the need to ensure that there is no interaction
between gaseous and particulate fumes.
For laboratory, sampling it is more common to use analytical gas
monitors rather than Draegar tubes.
With ozone monitoring it is also important to ensure that the
sampling lines are not susceptible to degradation by the gas.
For this reason, stainless steel and PTFE are the recommended
materials for these lines.
Test Procedure
Clean unpolluted air is allowed to enter the test chamber and a
weld sample is put in place. Monitoring is initiated and then
welding is started.
After welding and sampling has finished the air within the test
chamber is replaced to ensure that the next set of tests are not
affected by any residual gases.
Interpretation of Results
Once analysis and concentration of both particulate and gaseous welding fume have been measured, the total and elemental concentrations found can be compared with current exposure limits, and control measures, if appropriate, put in place.
Bulk or Laboratory Sampling of Particulate Fume
Bulk samples of particulate fume are taken by consumable manufacturers in their laboratories by means of an enclosed fume box, often referred to as a 'Swedish Fume Box' due to its country of origin.
The air and fume are drawn up through the box by some form of suction device, normally a portable fume extraction unit.
Measuring Gaseous Welding Fume
In welding and cutting the gaseous fumes of most concern are:
- Oxides of Nitrogen
- Ozone (O3)
- Carbon Dioxide (CO2); Carbon Monoxide (CO)
- Organic Gases
Measurement Techniques
Measurement of gaseous welding fume falls into two main categories, personal sampling and bulk or laboratory sampling.
Units of Measure
Gaseous fume is measured in ppm (parts per million) by means of chemical reaction tubes or electronic equipment, in a single-stage operation.
Personal Sampling of Gaseous Fume
The ready-calibrated detector tubes, about 100mm long, are normally made of glass, and are filled with chemical reagents, which undergo a colour change when exposed to a specific gas.
Each tube gives just one, instantaneous, reading and to obtain a time-weighted average sample, several tubes must be used, one after the other, over a known period of time.
Bulk or Laboratory Sampling of Gaseous Fume
The equipment required for the bulk analysis of gaseous fume tends to be much larger than that required for particulate fume because of the need to ensure that there is no interaction between gaseous and particulate fumes.
For laboratory, sampling it is more common to use analytical gas monitors rather than Draegar tubes.
With ozone monitoring it is also important to ensure that the sampling lines are not susceptible to degradation by the gas. For this reason, stainless steel and PTFE are the recommended materials for these lines.
Test Procedure
Clean unpolluted air is allowed to enter the test chamber and a weld sample is put in place. Monitoring is initiated and then welding is started.
After welding and sampling has finished the air within the test chamber is replaced to ensure that the next set of tests are not affected by any residual gases.
Interpretation of Results
Once analysis and concentration of both particulate and gaseous welding fume have been measured, the total and elemental concentrations found can be compared with current exposure limits, and control measures, if appropriate, put in place.