DCAN 12: Planning Control for Hazardous Substances
Exemption for small quantities of hazardous substances ("2% rule")
82. Regulation 4(7) of the Regulations provides an exemption under which small quantities of a hazardous substance may be disregarded when calculating the quantity of hazardous substances present at a site. Amounts not exceeding 2% of the relevant controlled quantity of a substance may be disregarded if their location at the site is such that they cannot act as an initiator of a major accident elsewhere on the site. The responsibility for determining whether such small quantities of hazardous substances are in a location which cannot act as an initiator of a major accident elsewhere on a site is, in the first instance, one for the site operator. In doing so, he will wish to take into account his responsibilities under the management of Health and Safety at Work Regulations. These Regulations require risk assessments to be made of the danger arising from the presence of these substances at the site and for the risk assessments to be submitted to HSENI . Site visits by HSENI inspectors will seek to ensure the exemption is not being abused.
83. This exemption does not apply to Chlorine, pressurised LPG, Hydrogen selenide or Selenium hexafluoride (substances numbered 6, 14, 35 and 39 in Part A of Schedule 3). The storage of Chlorine and pressurised LPG, even in such small amounts as 2% of their controlled quantities, is considered by HSENI always to present a significant off-site risk. For both Hydrogen selenide and Selenium hexafluoride, the controlled quantity at which a hazardous substances consent is required is 1 tonne. This is the amount which applying the 2% rule to these substances would allow to be disregarded. Therefore to maintain existing health and safety standards, it has been decided this exemption should not apply to these substances.