Every form of industrial and artisan work, during production, causes tiny pollutants (like dust, smoke, steam, etc.) which are then spread in the work place.
One good example is sawdust in a timber mill, or the release of solvents while varnishing or the fumes from welding.
The presence of chemical pollution in the work place can be of serious risk to the persons involved in relation to the levels reached.
These poisoning substances can be recognised as follows:
Dust, mist and fumes
Gas and Vapours
These terms refer to solid particles hanging in the air (often known as particulates).
This is a sort of dust caused by the fragmentation of a solid material. The finer the particulates the higher the risk for the worker.
The mist comes from tiny droplets formed from liquids due to processes of vaporization and condensation, for example, spraying. The fumes are made from any solid material that is vaporised at high temperatures, and this ‘vapour’ cools quickly and becomes a very fine particle.
To protect yourself from these fine mist and fume particulates the respirator can be adopted, which is certificated to regulation EN149. It is a device which has a filtering system similar to a net and it traps the particulates in such a way that they cannot pass the net mesh.
ATTENTION: Economical hygiene masks for larger particulates (with a diameter of more than 5 micron) not conform to Reg. EN149 and offer no protection, and by law are prohibited as a form of protection for people.
It must also be underlined that larger particles are always mixed with finer particles.
Cheap hygiene masks (uncertified) can prevent possible contamination of the worked product thus protecting the exterior environment from the user but NOT the person wearing the mask.
The matter here is the one of contaminating agents which behave exactly like the air and mix with the surrounding atmosphere.
Gas and vapour are made up of minute molecules which can penetrate the respirators, so the use of a chemical filter is vital, e.g. carbon filters for half-masks or full-faced masks, which act as a sponge against gas or vapour.
The highest risk comes from organic gas or vapour, e.g. solvents, paints, sprays and adhesives.
I “TLV” are the limit values of exposure as elaborated by the American Association of Hygienists (ACGIH), and indicate the following :
The maximum concentration of substances dispersed in the air to which a worker can be exposed to without any health risk;
the lower the TLV the more dangerous a substance, in that even a small quantity in the work place would cause a high risk situation.
Example: the TLV of cellulose is equal to 10 mg/m³. This means that the worker is not running risks with concentrations up to this level. In the case of copper dust and vapour the limit value is equal to 1 mg/m³: from this it can be deduced that copper dust is more dangerous than cellulose dust.
In order to simplify the pollutant levels in the work place, the ACGIH set out the TLV into 3 categories:
TLV-TWA (Threshold Limit Value – Time Weighted Average)
TLV-STEL (Threshold Limit Value – Short Term Exposure Limit)
TLV-C (Threshold Limit Value – Ceiling)
TLV-TWA: this is the limit value of extended exposure (the most important limit). This represents the average concentration, time considered, of pollutants present in the air in the work environment during a whole shift, being 8 hours a day, 5 days a week, for the whole of a person’s working life and that such exposure would not have any serious effects on them.
TLV-STEL: this is limit value for short term exposure. This shows the concentration that workers can be exposed to for a short period of time (max 15 minutes) without suffering irritation, chronic or irreversible tissue damage, or a reduction in the state of alertness which might increase the likelihood of injuries, or influence the ability to react in case of emergency, or effectively cut work efficiency.
TLV-C this is the top threshold value. This shows the concentration that must never be exceeded throughout a work-shift, not even for a moment. The TLV-C is only foreseen for a set of substances (making up almost a quarter of those indicated in the ACGIH table) of instant reaction, irritant to the mucous membrane or having a drugging effect, in such a way as to interfere with the self-control and attention levels of the worker, thereby being harmful to the same person (injuries) and damaging to the job the person is involved in.
|Substance||TLV-TWA (mg/m3)||TLV-STEL (mg/m3)||TLV-C (mg/m3)|
|Copper, Dust and Mist||1,00|
The Ministerial Decree of 2nd May 2001 (published in ‘Gazzetta Ufficiale’ n° 209, 8th September, 2001 – Ordinary supplement n° 226) sets the criteria for deciding the correct respirator to be used in different work places.
Therefore it is necessary to know
– The type of contaminant.
for non-hazardous solid and liquid particulates (dust, mist and fumes) the use of full or semi-faced masks is recommended (in case a full hermetic set is required).For Gas or Vapour, the use of full or semi-faced respirators with active carbon filters is recommended.
– Contaminant concentration.
A risk analysis the company has carried out in compliance with Law 626 which provides the amount of substance dispersal permitted in a certain environment, a value that has to be compared to the TLV for that substance, which can be easily found in manuals or security schedules of the substance in question.
In the case of non-hazardous solids and liquids (dust, mist and fumes):
If the concentration level is lower than the TLV: no individual protection is required.
If the concentration level is higher than the TLV and four times lower than the TLV: a FFP1 respirator must be worn.
If the concentration level is between 4 and10 times the TLV: a FFP2 respirator must be worn.
If the concentration level is between 10 and 30 times the TLV: a FFP3 respirator must be worn.
Cellulose particles TLV = 10 mg/m³
If the concentration level is less than 10 mg/m³: no protection is required.
If the concentration level is between 10 mg/m³ and 40 mg/m³: use mask FFP1
If the concentration level is between 40 mg/m³ and 100 mg/m³: use mask FFP2
If the concentration level is between 100 mg/m³ and 300 mg/m³: use mask FFP3
When the concentration level of the contaminant is unknown, in exceptional cases, a respirator can be selected based on the TLV values of the substance:
TLV > 10 mg/mc
0,1 < TLV < 10 mg/mc
TLV < 0,1 mg/mc