How does one purify barbecue utensils used for grilling pork in public gardens; and is it sufficient to light a fire in them before grilling to purify them and permit grilling halal meat in them?

If you doubt that utensils have been defiled by a pig, there is no harm in using them. However, if you are certain they have been defiled by it, they will not be purified except by washing. If utensils become defiled by cooking pork in them, their purification is by washing them seven times, one of which is with earth, by analogy with the impurity of a dog according to some scholars. In contrast, Sheikh Ibn Uthaymeen holds that the impurity of a pig is like other impurities, and washing it once is sufficient if the substance of the impurity has been removed. Furthermore, placing defiled utensils on fire or the drying of the impurity does not purify them; rather, they must be washed with water.