Performance Testing for the Corrosivity of Smoke

Abstract

The corrosivity of combustion products has arisen as an issue for both product manufacturers and standards bodies. While many industries can have concerns in this area, electronic communications and control equipment are especially vulnerable to the problem. The best way to manage the smoke corrosivity issue is to avoid a fire. In the event a fire does occur, a number of actions must be taken. An important consideration is that the materials and products used should have been chosen with due consideration of their corrosion-causing potential. To do this requires a suitable corrosivity test. It has traditionally been assumed that smoke corrosivity is directly correlated to the emission of acid gases. The results of recent experiments have shown that materials which do not release acid gases can, nevertheless, cause corrosion of metal surfaces, as determined by metal loss. In addition, for electrical equipment there are two other types of related nonthermal damage from combustion products which must be considered, viz., ohmic bridging and degradation of contacts. Laboratory tests proposed to date to measure the corrosive effects of combustion products all have significant deficiencies: some methods are not performance-based at all and are merely tests for pH. In others, unrealistic specimen heating or unrealistic exposure targets are used. To facilitate the development of a better test, a series of criteria have been developed. A specific test method was evolved from these criteria. The method is performance-based and incorporates realistic fire heating conditions.

Hydrogen chloride evolution from the heating of poly(vinyl chloride) compounds

“…The same formulation of material D was used for many other experiments, including smoke corrosivity testing [8,9], smoke toxicity testing z , the cone calorimeter (ASTM E 1354) rate of heat release test equipment ASTM round robin [10], a comparison of rates of heat release and of smoke release from a variety of materials [11,12] and a comparison of limiting oxygen index flammability testing [13]. Material E was prepared by cutting pieces of a telephone pedestal fabricated from a PVC compound, which had the formulation of material B.…”

Modern test methods for flammability

“…The Task Group made a number of recommendations, including the fact that it saw the need for a '3-part' target It was felt that in addition to measuring simple loss of metal, a practical test method should also measure two other aspects of non-thermal fire damage: ohmic bridging (which can short out electric circuits), and contact fouling (which can make relay and switch contacts non-functional). While the Task Group has not yet finished its work, it has commissioned a number of exploratory experiments and has proposed a candidate method [47]. Figure 7 shows the method as currently envisioned.…”

Exploratory research on nonthermal damage to electronics from fires and fire-suppression agents

“…The cone calorimeter has been used previously as a corrosimeter [8,9]. In earlier studies, various metal targets were exposed to smoke produced from different fuels burned in the cone calorimeter.…”