The internal cavities of Aga Cookers have historically been filled with loose-fill insulation. Inside the cooker body, there are lots of pockets and gaps around the cast iron conductions and burner casings etc. The insulation was poured inside after the build was complete, to rid the cooker of air pockets and insulate the cooker body. Diatomaceous Powder Insulation Early models of Aga cooker, like the Standard models made from the 1950's through to the Deluxe 1974 models (and some post-1974 models), would have originally contained Kieselguhr insulation power (or 'Diatomaceous Earth'). You can identify your model here. This is a fine, talc-like insulation, made from crushed up fossils called diatoms. It's satisfying to touch, but VERY messy to work with and instantly becomes thick clay once exposed to water or moisture. The good news is that amorphous diatomaceous earth is non-toxic. As with anything in powder or dust form - minimising exposure is key. You don't want to be breathing in lung-fulls of any dust or powder. If you're working with it, the proper PPE should be used; not just cloth or paper dust masks. Whilst the loose fill insulation may be ok, these models are still the most at risk for any asbestos exposure. AGA used asbestos rope seals inside their cookers for many years. These seals and gaskets are found inside the body of the older models explained above, and also around the lids and doors. Over the lifetime of these cookers, many of these gaskets and rope seals have been replaced for modern (safe) equivalents. AGA have previously reassured engineers and customers that undisturbed, these seals pose little risk and were of 'dust suppressed' or 'tightly woven' formats. Many of them have been exposed to moisture or grease over time which hardens them, meaning they're less friable in nature. They recommend that really old models of cooker are removed in one piece if possible and disposed of professionally.