Use the Bloom Accessibility Checker
When 
ePUB is selected in the 
Publish tab, a link labelled Accessibility Checker appears below Accessibility (under Settings).
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Click this link to open the Bloom Accessibility Checker dialog box.
You can leave this dialog box open as you correct problems and click the Refresh button to update the report.
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Click the Learn About Accessibility tab.
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Read the information about accessibility.
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Click the Accessibility Checklist tab.
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Fix any accessibility problems reported by a
(purple ?) or a 
(red X).
You may need to add image descriptions or record audio and so on.
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Click the Ace by DAISY Automated Checks tab.
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Wait for the progress information to finish and the Violations tab to appear.
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Fix any violations listed in Violations tab.
You can leave this tab open as you correct accessibility problems. Click the Refresh button to update the tab.
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Click and review information displayed in the Metadata, Outlines and Images tabs as desired or needed.
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