Cigarette Tar Testing Methods: Standards, Analytical Procedures, and Technical Requirements

Cigarette tar testing measures the nicotine-free dry particulate matter (NFDPM) in mainstream smoke, a key regulatory and quality-control parameter for tobacco products worldwide. This article explains the internationally recognized testing standards, sampling and conditioning procedures, machine-smoking regimes, and analytical methods used by accredited third-party laboratories to determine tar yields accurately and reproducibly.

Technical Overview

Tar, formally defined as nicotine-free dry particulate matter (NFDPM), is the condensed aerosol fraction of cigarette mainstream smoke trapped on a glass-fiber filter pad, minus its water and nicotine content. Because tar yield is one of the most closely regulated and communicated smoke constituents, its measurement is performed under strictly standardized machine-smoking conditions to ensure comparability between laboratories, production batches, and marketed products.

The reference method is ISO 4387, which specifies the determination of total particulate matter (TPM) and NFDPM using a routine analytical smoking machine, supported by ISO 3308 (smoking machine definitions and standard conditions), ISO 3402 (conditioning atmosphere), ISO 8243 (sampling), ISO 10362-1 (water by gas chromatography), and ISO 10315 (nicotine by gas chromatography). In China, the equivalent national standard is GB/T 19609 together with the corresponding GB/T methods for water, nicotine, and carbon monoxide in smoke. All testing should be carried out in laboratories operating in accordance with ISO/IEC 17025.

Testing Samples

Finished Marketed Cigarettes

Commercial cigarette products, sampled from production lines or retail channels according to ISO 8243, are tested to verify compliance with declared tar values, national tar ceilings, and labeling requirements. A representative sample of at least 100 cigarettes is typically drawn from each consignment for laboratory analysis.

Development and Prototype Products

Experimental cigarette designs, including new filter configurations, ventilation levels, paper porosities, and blend formulations, are screened for tar delivery during product development and harm-reduction programs before commercialization.

Reference and Control Cigarettes

Certified reference and monitor cigarettes are smoked alongside test samples to verify the performance of the smoking machine and the analytical system, as specified in ISO 16055, forming part of the laboratory's ongoing quality-control program.

Testing Items

A complete tar determination comprises the following measurable quantities, each expressed in milligrams per cigarette:

• Total particulate matter (TPM) captured on the Cambridge filter pad
• Water content of the smoke condensate
• Nicotine content of the smoke condensate
• Tar, calculated as nicotine-free dry particulate matter (NFDPM = TPM − water − nicotine)
• Puff count, butt length, and cigarette physical parameters recorded during smoking
• Carbon monoxide in the vapor phase (optional, determined simultaneously under ISO 8454)

Testing Methods

Sample Conditioning

Cigarettes are conditioned in a controlled atmosphere of 22 °C ± 2 °C and 60 % ± 5 % relative humidity for a minimum of 48 hours, as required by ISO 3402 and its GB/T equivalent. Smoking is also performed in an environment maintained within these limits. Correct conditioning is essential because moisture content significantly influences combustion behavior and tar delivery.

Machine Smoking under the ISO Regime

Conditioned cigarettes are smoked on a linear or rotary analytical smoking machine operated to ISO 3308 and ISO 4387: a puff volume of 35 mL, a puff duration of 2 seconds, and a puff interval of 60 seconds, using a bell-shaped puff profile. Smoking proceeds to a defined butt length, normally the tipping paper length plus 20 mm for filter cigarettes or 23 mm for non-filter cigarettes, whichever applies. Mainstream smoke is drawn through a pre-conditioned 44 mm Cambridge filter pad, which retains the particulate phase; typically 20 cigarettes are collected on a single pad for one determination.

Alternative Intense Smoking Regimes

For regulatory or research purposes, laboratories can also apply the Health Canada Intense (HCI) regime: a 55 mL puff volume, 2-second duration, 30-second interval, and 100 % blocking of filter ventilation holes. Because particulate loading is much higher, fewer cigarettes (commonly five) are collected per pad. Results under different regimes are not interchangeable and must always be reported together with the smoking conditions used.

Determination of Total Particulate Matter

The Cambridge filter pad is weighed to 0.1 mg before and after smoking on a calibrated analytical balance, and the mass gain yields TPM after correction for pad blanks. The pad is then extracted with isopropanol containing a suitable internal standard, such as n-heptadecane or anethole, to prepare the condensate solution for chromatographic analysis.

Water Determination

Water in the condensate extract is quantified by gas chromatography with a thermal conductivity detector (GC-TCD) in accordance with ISO 10362-1 or the corresponding GB/T method, following validation with calibration standards prepared in the extraction solvent.

Nicotine Determination

Nicotine in the same extract is quantified by gas chromatography with flame ionization detection (GC-FID) using an internal standard method, as specified in ISO 10315 and its GB/T equivalent. The method is calibrated with certified nicotine reference solutions over the working range.

Calculation and Reporting of Tar

Tar is calculated per cigarette as TPM minus water minus nicotine, with results normally reported to the nearest 0.1 mg per cigarette as the mean of replicate determinations. Where required, carbon monoxide in the vapor phase is measured simultaneously by non-dispersive infrared analysis under ISO 8454, allowing the full tar–nicotine–CO yield triplet to be reported. Each analytical sequence includes blank pads, control cigarettes, and duplicate determinations, with control charts maintained under the laboratory's ISO/IEC 17025 quality system.

Applications

Tar testing data serve a wide range of regulatory, industrial, and scientific purposes:

• Regulatory compliance verification against statutory tar ceilings, such as the 10 mg per cigarette maximum applied in the European Union under the Tobacco Products Directive and the tar limits enforced by other national authorities
• Verification of tar and nicotine yields printed on cigarette packs for consumer information and labeling compliance
• Release testing and statistical process control in cigarette manufacturing to keep deliveries within brand specifications
• Product development support, including optimization of filter efficiency, ventilation dilution, and paper permeability to engineer target deliveries
• Benchmarking and comparative studies of competing products on the market
• Scientific research into smoke chemistry, toxicant priority lists, and harm-reduction assessment frameworks promoted by the WHO Framework Convention on Tobacco Control

FAQ

What exactly is "tar" in cigarette testing?

Tar is the nicotine-free dry particulate matter (NFDPM) of mainstream smoke, obtained by subtracting the water and nicotine contents from the total particulate matter collected on a Cambridge filter pad during standardized machine smoking. It is a laboratory-defined quantity, not a single chemical substance.

Why are water and nicotine subtracted from total particulate matter?

Water and nicotine are quantified separately because they are individually measurable major constituents. Removing them yields a more stable and reproducible index of the remaining particulate condensate, which is the quantity regulated and labeled as tar.

What is the difference between the ISO and Health Canada Intense methods?

The ISO regime uses a 35 mL puff every 60 seconds with ventilation unobstructed, whereas the HCI regime uses a 55 mL puff every 30 seconds with all ventilation holes blocked, producing substantially higher yields. The two methods answer different questions and their results are never directly comparable.

Does machine-measured tar equal what a smoker actually inhales?

No. Machine yields are standardized comparative values obtained under fixed smoking parameters. Human smoking behavior varies with puff volume, frequency, and blocking behavior, so machine-measured tar is a product benchmark and regulatory metric rather than a measure of individual exposure.

How many cigarettes and how much time are required for a test?

A single determination typically collects 20 cigarettes on one pad under the ISO regime, with replicate determinations performed for statistical reliability. Including conditioning (at least 48 hours), machine smoking, extraction, chromatographic analysis, and reporting, a routine project generally requires several working days after sample receipt.

Which report details should a compliant test report contain?

A compliant report identifies the sampling basis, conditioning atmosphere, smoking regime (ISO or intense), puff parameters, butt length, cigarette counts, TPM, water, nicotine, and calculated NFDPM per cigarette, together with measurement uncertainty where applicable, and is issued under the scope of an ISO/IEC 17025 accredited laboratory.