The Customs Tariff provides for duty free entry of goods (and the articles and materials used in those goods) that are specifically designed for use by people with disabilities.
If you buy such goods while abroad, you will have to declare them. The goods would have to be classified under a tariff item in Chapters 1 to 97. Therefore, if the goods you buy meet the criteria of being specifically designed for use by people with disabilities, specify tariff item No. 9979.00.00 when you make your customs declaration so you do not have to pay the duty that might otherwise apply.
If you have questions about goods you are planning to import, visit the Canada Border Services Agency (CBSA) Web site, call 1-800-461-9999, or contact your nearest CBSA office. Staff at that office can explain any special requirements ahead of time, so that your goods clear customs quickly.