Legal Value

An Accredia certificate from Altiorlab srl has legal value because it is issued by the accredited laboratory on the basis of the decrees established by the Italian national calibration system.


Accredia is a signatory of the international mutual recognition agreements EA IAF and ILAC

Calibration and compliance

With the accreditation Accredia ISO 17025:2018 of Altiorlab srl declares its competence in the calibration of the optical particle counters, according to the international standard.

Certification becomes

a priority for the company

Accreditation of ALTIORLA SRL by ACCREDIA, according to the ISO / IEC 17025:2018 standard, means: Quality, reliability, competitiveness


Companies that choose to use the accredited calibrations of ALTIORLAB SRL, for products or services, see their image strengthened in terms of reputation and reliability of their commercial offer. They are more incisive on the market, by virtue of the formal recognition, by an independent subject, of skills and procedures consistent with international standards.


With the accreditation Accredia ISO 17025:2018 of Altiorlab srl declares its competence in the calibration of the optical particle counters, according to the international standard.

Quality assurance

The calibration certificate of ALTIORLAB SRL, which accompanies a product or service, certifies that the supplier has fulfilled all the obligations required to place on the market a reliable and quality service or good, according to internationally recognized standards such as ISO 21501-4:2018 for the calibration of the particle optical meters.

More trust, less risk

The consumer can trust the products and services calibrated by the accredited laboratory ALTIORLAB SRL, because they meet stringent international requirements, and reduce the risks associated with consumption.

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The best investment

for companies of today and tomorrow

For institutions, businesses and consumers, the benefits of accreditation are represented by the advantages they acquire when they choose to rely on conformity assessment services issued by accredited laboratories such as ALTIORLAB SRL


Increase business


Consulting provided
on calibrations


Certifications of compliant


Years of industry

Calibrations performed in the company

or at the customer's company

Service available for all the counters of all brands; PMS, MET One, Lighthouse, Climet, etc..





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The ISO 21501-4:2018

in detail

This Second edition cancels and replaces the first edition (ISO 21501-4:2017), which has been technically revised.

The main changes from the previous edition are:

    • Clause 4 for “Principle” and Clause 5 for “Basic configuration” have been added;
    • “size calibration” and “verification of size setting” have been combined as “size setting error” in the requirements clause;
    • “Test report” has been changed to 6.10 on “Reporting of test and calibration results”;
  • Information about uncertainties has been enriched and is now the subject of Annex E:
      1. size setting error;
      1. counting efficiency;
      1. sampling flow rate error;
      1. size resolution (with the particle size used);
    1. false count.

A calibration certificate shall furthermore include:

  1. identification;
  2. relevant enviromental conditions;1
  3. a stade uncertainty for each result 1 to 4 with reference to the calculation method ( e.g. ISO/IEC Guide 98-3);
  4. a stade false count at 95% confidence limit.

NOTE: Calibration certificates issued by ISO/IEC 17025:2018 accredited laboratories and covering all results for the parameters 1 to 5 are considered to comply with the requirements above.

ist of all parts in the ISO 21501-4:2018 series can be found on the ISO website


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QS Group srl is an active and well integrated company in a range of activities whose aim is the control of airborne particulate and microbiological contamination in environments and production processes at risk in a wide production scenario. Control tools always up-to-date, partnership with leading international companies, service procedures always up-to-date with current regulations allow QSGroup srl to provide customers with cutting-edge solutions and services.

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Via Torquato Tasso, 5, 20825 Barlassina MB

At 700 meters from the Seveso station
15 minutes from Milan
30 minutes from Malpensa and Linate