The type of air purifier you need will depend on your specific needs and the size of the room or area you want to purify. Here are some factors to consider when choosing an air purifier:

Room Size: The size of the room or area you want to purify will determine the size and capacity of the air purifier you need. Air purifiers are rated based on the size of the room they can effectively purify, so it's important to choose a purifier that is appropriate for the size of your space.

Type of Filter: The type of filter used in the air purifier is also important. HEPA filters are the most common type of filter used in air purifiers and are effective at removing small particles like dust, pollen, and pet dander. Some air purifiers also use activated carbon filters to remove odors and volatile organic compounds (VOCs) from the air. Besides, photocatalyst filter is also a good option which can decompose bacteria and viruses into harmless substance.

Noise Level: Some air purifiers can be quite noisy, which can be disruptive to sleep or other activities. Look for an air purifier with a noise level that is comfortable for your needs.

Additional Features: Some air purifiers come with additional features like air quality sensors, automatic shut-off, APP, child lock, timer and so on. These features can be useful but may also add to the cost of the purifier.

Price: Air purifiers can vary widely in price, so it's important to choose a purifier that fits your budget. Keep in mind that higher-priced air purifiers may offer more features or better performance, but may not be necessary for all users.

Overall, it's important to choose an air purifier that meets your specific needs and fits your budget. Consider the factors above and do some research to find the best air purifier for your situation.