ISO/DIS 5622:2025(en)

ISO/TC 126

Secretariat: DIN

Date: 2025-05-27

Tobacco Heating System — Determination of carbon monoxide in the vapour phase of tobacco heating system aerosol — NDIR method — Electrically heated tobacco products (eHTPs)

Système de tabac chauffé — Dosage du monoxyde carbone dans la phase gazeuse de l’aerosol d’un système de tabac chauffé — Méthode IRND — Partie 1 : Système de tabac chauffé électriquement (eHTP) portée

© ISO 2025

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Contents

Foreword iv

Introduction v

1 Scope 1

2 Normative references 1

3 Terms and definitions 1

4 Principle 1

5 Apparatus 2

5.1 A conditioning enclosure, maintained accurately in accordance with the conditions specified in ISO 5501, for conditioning the HTP sample prior to smoking 2

5.2 Barometer, capable of measuring atmospheric pressures to the nearest 0,1 Kpa 2

5.3 Thermometer, capable of measuring temperature to the nearest 0,1 °C 2

6 Reagents 2

7 Procedure 2

7.1 Conditioning 2

7.2 NDIR analyzer calibration 3

7.3 Aerosolization and collection of the gas phase 3

8 Expression of results 3

8.1 Calculation of the average volume of carbon monoxide per consumable of tobacco heating system 3

8.2 Calculation of the average mass of carbon monoxide per HTP 4

9 Repeatability and reproducibility 4

10 Test report 5

10.1 General 5

10.2 Characteristic data about the samples and samples identification 5

10.3 Sampling 5

10.4 Description of test 5

10.5 Test results 6

Bibliography 7

Foreword

ISO (the International Organization for Standardization) is a worldwide federation of national standards bodies (ISO member bodies). The work of preparing International Standards is normally carried out through ISO technical committees. Each member body interested in a subject for which a technical committee has been established has the right to be represented on that committee. International organizations, governmental and non-governmental, in liaison with ISO, also take part in the work. ISO collaborates closely with the International Electrotechnical Commission (IEC) on all matters of electrotechnical standardization.

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This document was prepared by Technical Committee ISO/TC 126, Tobacco and tobacco products.

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Introduction

Tobacco heating systems (THS) are designed to heat a tobacco substrate, to produce a nicotine-containing aerosol without the combustion of the tobacco substrate. A THS is a combination of a heated tobacco product (HTP) and a tobacco heating device (THD). The HTP part of the THS is a product containing a tobacco substrate that is designed to be heated and not combusted.

With the emerging development and commercialisation of HTPs, there are a number of different approaches to heating the HTP, categorised as electrically, aerosol and carbon, HTPs; eHTP, aHTP and cHTP, respectively as described in ISO 6080^[1].

The method in this document is based upon CORESTA recommended method CRM 108^[2] which was written on the basis of the results obtained in an interlaboratory study conducted in 2021 involving seventeen laboratories and four THS samples. The results of this interlaboratory study were published by CORESTA in a technical report HTP-280-CTR.^[3] The results showed repeatability and reproducibility values for aerosol heated tobacco products (aHTPs) were not statistically relevant. Carbon heated tobacco products (cHTPs) has not been commercially available.

This document defines and specifies the requirements for an electrically heated tobacco product (eHTP) for the quantification of carbon monoxide in the vapour phase of the aerosol.

No machine puffing regime can represent all human puffing behaviour.

— It is recommended that eHTP also be tested under conditions of a different intensity of machine puffing than those specified in this document.

— Machine puffing testing is useful to characterize eHTP emissions for design and regulatory purposes, but communication of machine measurements to users can result in misunderstandings about differences in exposure and risk across brands.

— Aerosol emission data from machine measurements may be used as inputs for product hazard assessment, but they are not intended to be nor are they valid

IMPORTANT — This document is a reference document for ISO standards and measurement on tobacco heating systems (e.g. ISO 6080). Regulation and standardisation are independent from each other, and standardisation does not pre-empt regulation.

Tobacco Heating System — Determination of carbon monoxide in the vapour phase of tobacco heating system aerosol — NDIR method — Part 1: Electrically heated tobacco products (eHTPs) scope

WARNING — The use of this document can involve hazardous materials, operations and equipment. This document does not purport to address all the safety problems associated with its use. It is the responsibility of the user of this document to establish appropriate safety and health practices and determine the applicability of any other restrictions prior to use.

This document specifies a method for the determination of carbon monoxide (CO) in the vapour phase of Tobacco Heating System (THS, as described in ISO 6080) aerosol.

NOTE If tested products provide CO levels outside of the upper limit of the calibration range described in this document, then ISO 22947 applies.

The following documents are referred to in the text in such a way that some or all of their content constitutes requirements of this document. For dated references, only the edition cited applies. For undated references, the latest edition of the referenced document (including any amendments) applies.

ISO 5501‑1, Tobacco heating systems — Definitions and standard conditions for aerosol generation and collection — Part 1: Electrically heated tobacco products (eHTPs)

For the purposes of this document, the following terms and definitions and the terms and definitions in ISO 6080 apply.

ISO and IEC maintain terminology databases for use in standardization at the following addresses:

— ISO Online browsing platform: available at https://www.iso.org/obp

— IEC Electropedia: available at https://www.electropedia.org/

3.1

vapour phase

portion of aerosol, which passes the particulate phase trap during aerosol collection in accordance with ISO 5501‑1

3.2

clearing puff

any puff taken immediately after a THS has been stopped or removed from the holder

[SOURCE: ISO ISO 5501-1:2024, 3.13]

Aerosol generation shall be performed in accordance with the procedures given in ISO 5501‑1. Collection of the vapour phase of the aerosol and measurement of the carbon monoxide using a non-dispersive infrared (NDIR) analyser calibrated for carbon monoxide. Calculation of the amount of carbon monoxide mg per HTP.

Usual laboratory apparatus, and particularly the following items.

5.1 A conditioning enclosure, maintained accurately in accordance with the conditions specified in ISO 5501, for conditioning the HTP sample prior to smoking

5.2 Barometer, capable of measuring atmospheric pressures to the nearest 0,1 Kpa

5.3 Thermometer, capable of measuring temperature to the nearest 0,1 °C

5.4 A standard machine for routine analytical generation and collection of aerosol and gas from THS complying with ISO 5501‑1 as appropriate.

5.5 A system for the collection of the total gas phase satisfying the following conditions:

5.5.1 It should not interfere with the normal performance of the machine.

5.5.2 It shall be constructed and maintained so that the carbon monoxide content of the gas phase sample does not change by more than 5 % over a period of two hours for those values above LOQ. The collection container shall be checked with the highest gas mixture calibration. To check the impermeability of the vapourphase collection container, the CO concentration shall be measured immediately after filling the preouvly evacuated vapour-phase collection container and a second time after a period of 2 h. The measured value of the CO concentration shall not differ by more than 5 % from the first and second determination.

5.5.3 Gas bag volume shall be chosen according to the actual aerosolization conditions and shall be at least equal to the final volume of the gas phase plus clearing puffs, but it is recommended that it does not exceed twice that final volume.

5.5 A non-dispersive infrared analyzer satisfying the manufacturer’s instructions and the following conditions:

5.5.1 Range of measurement: An instrument of sufficient range to accommodate expected sample values, which can depend on the number of clearing puffs used to dilute the sample. For undiluted gas samples a range as low as 0 ppm to 1 000 ppm has been determined to be sufficient. Alternative ranges are acceptable provided that the performance specifications given in paragraph 5.3.2 are equalled or exceeded.

5.5.2 Linearity: ≤ ±1 % full scale (≤ 10 ppm), Resolution: 1 ppm or better, Repeatability: ≤ +1 %/– 0,5 % full scale (≤ 5 ppm), Limit of detection: ≤ 0,5 % full scale (≤ 5 ppm) determined over the normal measurement period and under conditions of constant temperature and pressure.

5.5.3 The response to 10 % (v/v) of carbon dioxide shall not exceed 2,0 ppm as carbon monoxide. The response to 2 % (v/v) of water vapor shall not exceed 20 ppm as carbon monoxide.

Note: conversion factor between % and ppm is as follow 1 % = 10 000 ppm

CO Standard Gases: At least two standard gas mixtures of accurately known concentration in nitrogen covering a range from 0 to 1 000 ppm as per 5.3.1 should be utilized. A single concentration should be used for calibration and both two gases should be used for verification purposes. The standard gases must be guaranteed by the supplier to be better than 2 % (relative). Make up gases other than nitrogen, such as helium, must not be used as the detector response for carbon monoxide will be different.

Temperature equilibrated in sealed packs according to the time and environmental conditions specified in ISO 5501-1 and removed from the pack immediately prior to testing.

7.2.1 After warming up the instrument according to the manufacturer’s recommendations, purge the instrument with air and adjust to read zero.

7.2.2 Fill a previously evacuated gas phase collection container with CO of a concentration on the upper level of your expected CO range, re-evacuate and refill with the same gas. Ensure that the gas in the container is at ambient temperature and pressure. Introduce the gas into the measuring cell of the analyzer using the system sampling pump. Note the value when a steady reading has been obtained.

7.2.3 If necessary, adjust the instrument reading to agree with the certified value of the standard gas.

7.2.4 Repeat 7.1.2 for the other standard gas. If there is a difference greater than 5 % between the observed and specified values, attention should be given to the analyzer linearity.

7.2.5 Establish the relationship between the readings and the actual carbon monoxide concentrations in the standard gases at least weekly. This must be linear within the limits reported in Clause 5. Non-linearity indicates that there is an instrument problem.

7.2.6 Check the calibration prior to measurement using the standard gas utilized in step 7.1.2. If there is a difference greater than 5 % between observed and expected values repeat the full calibration (7.1).

7.3.1 Devices should be fully charged and cleaned according to manufacturer’s instructions before the aerosolization and collection. Typically, the number of consumables is at minimum two and at maximum five per replicate for eHTP.

NOTE THDs may be reused for generation of aerosol from multiple HTP samples.

The characteristic data and sampling details of the THDs shall be recorded according to 10.2 and 10.3.

7.3.2 Proceed in accordance with the instructions pertinent to the equipment used. Ensure that the collection device is properly evacuated before the start of aerosolization. There must not be any residual vacuum upstream of the collection device before initiating the run.

7.3.3 Set up the machine and aerosolize the samples in accordance with ISO 5501‑1. Consider any other applicable manufacturer-specific instructions.

7.3.4 After completion of the sample aerosolization, remove the sample and take one clearing puff between consumables, and five clearing puffs at the end of the collection after the final consumable is removed from the port of the machine.

7.3.5 Record the total number of puffs (i.e., aerosolization puffs and clearing puffs) taken on each port.

7.3.6 Measure the carbon monoxide content of the collected gas phase.

7.3.7 Recheck the calibration of the analyzer (see 7.1.6.) on each day of testing and introduce the gas phase into the measuring cell of the analyzer under the same conditions of sampling and ambient temperature and pressure and the same gas flow rate as used during calibration. Read the analyzer output and determine the observed carbon monoxide concentration.

7.3.8 At the end of each run, the gas phase collection container must be emptied and flushed with air. The apparatus is then ready for the next run starting at 7.2.1.

The average volume of carbon monoxide per consumable, V_as, expressed in millilitres, is given by the Formula (1):

(1)

where

C is the percentage by volume of carbon monoxide observed;

V is the puff volume, in millilitres;

N is the number of puffs in the measured consumables (including clearing puffs);

p is the ambient pressure, in kilopascals;

p₀ is the standard atmospheric pressure, in kilopascals;

S is the number of consumables item aerosolized;

T₀ is the temperature for the triple point of water, in Kelvin;

t is the ambient temperature, in degrees centigrade.

In the calculation, the following values can be used:

V = 55 ml and rounded values of p₀ (101,3 kPa) and T₀ (273 K).

NOTE If the instrument reading is in ppm, 100 ppm = 0,01 %.

This conversion shall be used to express the C in %.

The average mass of carbon monoxide per consumable, m_cons, expressed in milligrams, is given by the Formula (2):

(2)

where

M_CO is the molar mass of carbon monoxide, in grams per mole;

V_m is the molar volume of an ideal gas, in litres per mole.

In the calculation, the following values can be used:

Rounded values of M_CO (28 g/mol) and V_m (22,4 l/mol).

Carbon monoxide results listed in the Table 1 below are based on the study “Proficiency Study for Propylene Glycol, Glycerin, Nicotine, CO, NO, NOx, ACM, and DML in HTP Aerosol”^[3] conducted by CORESTA using two eHTPs. The statistical analysis was conducted in basic conformance with ISO 5725‑2.^[4] All participating laboratories in the proficiency study used NDIR method for CO analysis.

Table 1 — Estimates given by data analysis

The test report shall give the carbon monoxide content of the sample (i.e. per consumable, per puff, etc.). The test report shall also mention all pertinent operating conditions not specified in this document as well as any circumstances that may have affected the result.

The test report shall show the method used and the results obtained. It shall also mention any operating conditions not specified in this document or regarded as optional, as well as any circumstances that may have influenced the results. The test report shall include all details required for complete identification of the sample. If appropriate, the information listed in 10.2 to 10.5 shall be recorded.

All necessary details to describe the samples fully such as:

a) name of the HTP manufacturer;

b) name of the THD manufacturer;

c) country of sampling;

d) HTP product name;

e) THD product name;

f) HTP packet identifier (of that product sampled that day);

g) THD packet identifier (of that product sampled that day).

All necessary details to describe the sampling fully such as:

a) type of sampling procedure;

b) number of HTPs in laboratory samples

c) date of sampling (HTP and THD);

d) place of purchase or sampling (HTP and THD).

All necessary details to describe the test fully such as:

a) a reference to this document, i.e. ISO 5622:2025;

b) date of test;

c) type of aerosol generation machine used;

d) type of analyser used;

e) total number of HTP consumables tested;

f) number of HTPs aerosolised into each collection device;

g) number of devices to aerosolise the HTP for all aerosol collection replicates;

h) room temperature (°C) during testing;

i) relative humidity (%) during testing;

j) atmospheric pressure (kPa) during testing.

The expression of the laboratory data depends on the purpose for which the data are required, and the level of laboratory precision. Confidence limits shall be calculated and expressed on the basis of the laboratory data before any rounding has taken place:

— number of puffs per consumable taken;

— observed carbon monoxide concentration, expressed as a percentage by volume, for each channel, to the nearest 0,01 %, and the average per HTP, to the nearest 0,1 %;

— amount of carbon monoxide determined, in milligrams per 100 mL HTP for each channel, to the nearest 0,1 mg, and the average per HTP, to the nearest 1 mg/100 mL.

Bibliography

[1] ISO 6080, Tobacco heating systems — Vocabulary

[2] CORESTA Recommended Method CRM-108 – Determination of Carbon Monoxide from Heated Tobacco Products with a Non-Dispersive Near Infrared Analyzer

[3] CORESTA Technical Report – Proficiency Study for Propylene Glycol, Glycerin, Nicotine, CO, NO, NOx, ACM, and DML in HTP Aerosol – HTP-280-CTR

[4] ISO 5725‑2, Accuracy (trueness and precision) of measurement methods and results — Part 2: Basic method for the determination of repeatability and reproducibility of a standard measurement method

[5] ISO 22947, Cigarettes — Determination of carbon monoxide in the vapour phase of cigarette smoke with an intense smoking regime — NDIR method