Quest for Testing Procedures for Heated Tobacco Products

How a Cambridge Pad looks following ‘smoking’ of a THP product.

Essentra

How a Cambridge Pad looks following smoking of a conventional cigarette.

Essentra

Quest for Testing Procedures for Heated Tobacco Products

Tests currently in use were not wholly applicable.

Story by Essentra

Standards for testing combustible cigarettes have been well defined for many years, but for e-cigarettes and next generation products, less so. Rigorous tests for water, nicotine and nicotine free dry particulate matter (NFDPM) were already in place for combustibles, but corresponding test categories for e-cigarettes and e-liquids were very limited.

Now, Tobacco Heated Products (THP) have broken new ground. They were ground breaking when they were first introduced to the market; the heat sticks were designed with longer filter lengths, unique configurations, new materials and relatively low draw resistance. Also, the filter components were able to achieve relatively low filtration whilst maximising vapour temperature reduction. With this in mind, it became apparent that the current tests were not wholly applicable and new methods and tests themselves for THP products would have to be developed.

Essentra, the leading global supplier of filters and analytical testing, recently conducted an intensive study in its Essentra Scientific Services to discover the best methods to test THP and ensure that the tests provided useful and accurate data. Various areas were explored, including:

• How to enable a THP to be smoked on a standard linear smoking machine ;

• What the most appropriate smoking regime is to adopt for THP;

• How to develop a method to measure vapour temperature;

• Understanding ‘NFDPM’;

• Understanding the function of the filter element and its individual elements; In deciding what smoking regime

to use, it was important to consider the length of time a heating device was active, which system was best to produce the most accurate data, and the ways to collect enough material to analyse the water, nicotine, NFDPM and carbon monoxide.

Though the creation of a new smoking standard was considered, a recognised industry smoking method was ultimately chosen. The Canadian intense smoking method—where a 55ml puff is taken over two seconds every 30 seconds—was used for analysis, smoking four channels, three heat sticks per channel with six puffs per heat stick.

The use of six puffs was settled upon to ensure that the 44mm Cambridge filter pad, which has a limit of 150mg of material, did not overload. In addition, the analysis of water and nicotine was conducted using the standard ISO method 4387, resulting in the NFDPM.

NFDPM is very different in a THP— you can see the difference in colour, which most likely results from the reduced constituents in ‘smoke’ due to the lack of combustion.

THP-heating devices have a core temperature in excess of 200°C. The filter element without tip ventilation needs to reduce the vapour temperature to a level acceptable to the consumer (normally about 35–50°C). Thermal measurement of vapour proved to be the most challenging with existing smoking machine setups due to the difficulty in observing the vapour being drawn from the heat stick at the point of smoking.

In order to measure the vapour temperature during the smoking cycle, Essentra designed a device which enabled the measurement of the temperature emitted from the end of the heat stick during smoking. This also offers the capability to measure each individual filter segment, allowing an understanding of the filtration and thermal performance of different filter styles and materials, and the impact on ventilation in THPs.

The study required the modification of a linear smoking machine and the development of a device to measure the filtration and thermal performance of the heat stick, it helped to enhance Essentra’s knowledge and understanding of the topic. By developing its bespoke filter solutions for THP, Essentra may be able to widen its portfolio further in the future, including simpler filter assemblies and biodegradable filter components. [TI]