Table 21 summarises the choices of different types of gas safety interlocks for schools. Table 21 Summary of interlock requirements according to appliance type. Interlock Appliance Appliance Appliance Comments system type Type A Type B Type C Flow switch Yes Yes as a Not Simple system. Does or air primary needed not prove pressure interlock environmental switch conditions. Mechanical Yes Yes as a Not Simple system, may ventilation primary needed be slightly better fan power interlock than Does not monitoring prove environmental conditions. CO2 Yes Yes as a Not For legal reasons not monitoring secondary needed permitted alone with interlock Type B. Provides but only positive proof/control with a of the environment primary for Type A. Suitable interlock system for teaching spaces in which there are only Type A appliances. Easy to apply in schools having environmental control system. Variable Yes Yes as a Not Reduces power Speed Drive secondary needed consumption and fan with CO2 interlock noise through monitoring but only demand controlled and control with a ventilation. primary Most suitable system interlock for teaching spaces in which there are only Type A appliances. Central school catering must comply with IGEM UP 19 and BS 6173.
Table 21 summarises the choices of different types of gas safety interlocks for schools. Table 21 Summary of interlock requirements according to appliance type. Interlock system type Appliance Type A Appliance Type B Appliance Type C Comments Flow switch or air pressure switch Yes Yes as a primary interlock Not needed Simple system. Does not prove environmental conditions. Mechanical ventilation fan power monitoring Yes Yes as a primary interlock Not needed Simple system, may be slightly better than Does not prove environmental conditions. CO2 monitoring Yes Yes as a secondary interlock but only with a primary interlock Not needed For legal reasons not permitted alone with Type B. Provides positive proof/control of the environment for Type A. Suitable system for teaching spaces in which there are only Type A appliances. Easy to apply in schools having environmental control system. Variable Speed Drive with CO2 monitoring and control Yes Yes as a secondary interlock but only with a primary interlock Not needed Reduces power consumption and fan noise through demand controlled ventilation. Most suitable system for teaching spaces in which there are only Type A appliances. Central school catering must comply with IGEM UP 19 and BS 6173.