20 Most Recent LG LFX25991ST 24.6 cu. ft. Counter-Depth French Door Refrigerator with SpiProtector Glass Shelves, Humidity Crispers, Glide N Serve Drawer, 3-Tier Freezer and External Ice/Water Dispenser - Page 5 Questions & Answers

As errors and fixes vary by brand at least and sometimes by model as well, that minimum information is posted with a query. On some models, it would mean that the filter needs replacement, that its filtration ability had fallen below an acceptable threshold. On others, it would mean that pollution has been detected. The user manual should indicate what it means. Possibly, you might find information at the brand site or at a user manual site or just by Googling "brand model air purifier red light"

replce the mtors as there is nothing in them to clean