Proposed Change 2145

Some fire point data for water-miscible liquid mixtures (WMLMs) that appear in the National Fire Code of Canada (NFC) were taken directly from technical reports or papers, while others were estimated by adding 10°C to the flash point. However, the WMLM classifications in the NFC that are based on estimated fire points may not be accurate. Testing could yield different classifications than those in Table A-4.1.2.2., for example, which may confuse Code users.

The open-cup fire point test indicates the temperature at which vapours sustain continuous combustion for at least five seconds. While the open-cup fire point can be a useful measure, it may not be the best method for classifying WMLMs. Moreover, open-cup fire points are not consistently documented or included in safety data sheets, which makes such data hard to find and less user-friendly.

This proposed change specifies the that WMLMs should be classified in the same manner as other flammable and combustible liquids, using closed-cup flash points rather than the open-cup fire point method previously set out in the NFC. 

To more accurately assess the fire risk associated with WMLMs and bring the NFC into alignment with other regulations, updates should be made to the test method for classifying these liquids in the NFC. This proposed change would classify them according to their closed-cup flash point.

The closed-cup flash point test is the global standard for fire risk assessment. This test method provides realistic hazard simulation by mimicking confined spaces, such as storage tanks and containers, where flammable vapours build up. The closed-cup flash point is used by the US Occupational Safety and Health Administration (OSHA), the US Department of Transportation (DOT), the National Fire Protection Association (NFPA), the Globally Harmonized System of Classification and Labelling of Chemicals (GHS), and the current NFC for the classification of flammable and combustible liquids. It should also be applied to WMLM classification.

To assess the fire risk posed by flammable WMLMs, closed-cup flash point data based on experiments or reliable literature should be used, avoiding assumptions and estimations.

Of the five WMLMs currently listed in NFC Sentence 4.1.2.2.(1) (mixtures of methanol, ethanol, 2-propanol, acetone and acetic acid and water), none have a boiling point below 37.8°C (see Table 1). This means that none are classified as Class IA flammable liquids. The WMLMs posing the highest risk would be classified as Class IB flammable liquids.

Table 1. Boiling Point of Solvents

This proposed change updates the classification of WMLMs in NFC Table 4.1.2.2. based on closed-cup flash point testing. The test data for each WMLM are discussed below.

1. Methanol

Sample mixtures of methanol and water were prepared at different concentrations and sent to Health Canada for closed-cup flash point testing. Figure 1 plots the flash points obtained by Health Canada against the literature values.

Figure 1. Closed-cup flash points of methanol-water mixture

The literature values in Figure 1 can be found in Table 2.

Table 2. Closed-Cup Flash Points of Methanol-Water Mixture from Literature [1]

As demonstrated in Figure 1, the experimental data from Health Canada are in reasonable alignment with the values from the literature.

2. Ethanol

Similarly, sample mixtures of ethanol and water at different concentrations were tested by Health Canada to determine their closed-cup flash points, which are cross-referenced with the values based on published literature in Figure 2 [2].

Figure 2. Closed-cup flash points of ethanol-water mixture

The literature data in Figure 2 can be found in Table 3.

Table 3. Closed-Cup Flash Points of Ethanol–Water Mixture from Literature [2]

As demonstrated in Figure 2, the experimental data from Health Canada are in close alignment with that from the literature.

3. 2-Propanol

Sample mixtures of 2-propanol and water at different concentrations were tested by Health Canada to determine the closed-cup flash points, which are cross-referenced with the values based on published literature in Figure 3 [1].  

As shown in Figure 3, the experimental data from Health Canada confirm the reliability of the data from the literature [1].

4. Acetone

The closed-cup flash points of the acetone–water mixture at different concentrations can be found in Reference [3]. Figure 4 and Table 5 summarize the data.

5. Acetic Acid

References

[1] Astbur G., Bugand-Bugandet J., Grollet E., and Stell K., “Flash Points of Aqueous Solutions of Flammable Solvents,” IChemE Symposium Series No. 150, pp. 1–18, 2004.
[2] National Fire Protection Association, Fire Protection Guide to Hazardous Materials, Eds. Spencer A.B. and Colonna G.R., 2002.
[3] Janès A. and J. Chaineaux, “Experimental Determination of Flash Points of Flammable Liquid Aqueous Solutions,” Chemical Engineering Transactions, vol. 31, 2013.

The impact of this proposed change is expected to be minimal.

The deletion of the classification of the acetic acid and water mixture in this proposed change would provide relief for Code users who handle and store acetic acid and water mixtures as currently required by the NFC. For example, a mixture of 10% acetic acid and water is commonly used and sold as “cleaning vinegar” in Canada. Any acetic acid and water mixture with a concentration of acetic acid higher than 8% by volume is currently classified as a Class IB liquid in the NFC, so restrictions regarding maximum quantities, clearance and storage location have to be followed instead of Part 4 requirements, which could be more stringent than necessary in sprinkler protection, spill containment, etc. 

Due to the variety of real-life situations, however, the exact or average compliance cost savings cannot be calculated.

This proposed change can be enforced by the infrastructure currently available. The proposed change simply updates the test method and the classification of WMLMs in the NFC.

Regulators, engineers, building owners, contractors, fire services, and certain businesses using and storing WMLMs.