Xiaomi Air Purifier 4 Compact Manual & Setup Guide

ruminesia – Setting up the Xiaomi Air Purifier 4 Compact only takes a few basic steps, but one mistake can stop the purifier from working properly. The most common one is simple: turning the device on before removing the protective plastic from the filter.

This Xiaomi Air Purifier 4 Compact manual covers the complete setup process, control buttons, operating modes, PM2.5 indicator colors, Xiaomi Home app connection, Wi-Fi reset, cleaning, filter replacement, and common troubleshooting steps. The device uses model number AC-M18-SC, has a 230 m³/h Particle CADR, and is designed for an effective coverage area of 16–27 m².

Key Highlights

• Xiaomi Air Purifier 4 Compact model AC-M18-SC covers around 16–27 m².
• Its 230 m³/h Particle CADR is better suited to bedrooms and smaller rooms.
• The purifier supports Auto, Sleep, and Manual modes.
• The PM2.5 indicator changes between green, yellow, orange, and red.
• Xiaomi Home connects to the purifier through 2.4 GHz Wi-Fi.
• The AFEP7TFM01 replacement filter is designed to last around 6–12 months.
• Keep at least 20 cm of clearance between the air inlets and nearby walls or objects.

1. Xiaomi Air Purifier 4 Compact Overview & Official PDF Manual

The Xiaomi Air Purifier 4 Compact is a small smart air purifier with a cylindrical design, 360-degree air intake, Xiaomi Home connectivity, and a three-layer filtration system. Xiaomi lists the device under model AC-M18-SC, with dimensions of 220 × 355 mm and a net weight of approximately 2.2 kg.

If you are looking specifically for the manual, you can use the official Xiaomi documentation below:

Download the official Xiaomi Air Purifier 4 Compact PDF manual

Xiaomi also provides a regional online user guide for the same model.

Xiaomi Air Purifier 4 Compact Specifications

Xiaomi’s specifications list a maximum rated power of 27 W, while its product information states that Sleep Mode operates at around 20 dB. The replacement filter compatible with this model is AFEP7TFM01.

What’s in the Box & Control Panel

The standard package includes the purifier, filter, power cord, and user manual. The top control panel has three physical controls:

The device also uses separate indicators for child lock, operating mode, Wi-Fi, filter exhaustion, and air quality. Child Lock is a function activated through the Mode button rather than a separate physical button.

2. How to Set Up the Xiaomi Air Purifier 4 Compact

Before turning on the Xiaomi Air Purifier 4 Compact for the first time, remove the protective plastic packaging from the filter. The filter is located inside the bottom compartment of the purifier. Follow these steps:

1. Open the filter compartment. Turn the purifier over and access the filter compartment at the bottom.
2. Remove the filter. Take the filter out of the compartment.
3. Remove the protective plastic. Make sure all plastic packaging around the filter has been removed.
4. Reinstall the filter. Place the filter back into the compartment correctly.
5. Close the filter compartment. Make sure the compartment is properly secured.
6. Connect the power cord. Plug the supplied power cord into the purifier and then into an electrical outlet.
7. Turn on the purifier. Press the Power button on the top panel.
8. Connect Xiaomi Home. Install the Xiaomi Home app and add the purifier through the app if you want smartphone controls.

The purifier cannot operate correctly if the filter compartment cover or grille is not installed properly. Xiaomi also recommends using the supplied power adapter and turning the purifier off and unplugging it before maintenance.

Optimal Placement: Table or Floor?

The Xiaomi Air Purifier 4 Compact can be used on a table or floor, but placement matters more than the surface itself. Xiaomi recommends leaving at least 20 cm of space between the air inlets and nearby walls or objects.

Avoid placing the purifier where curtains, furniture, clothes, or other objects block the air intake. For better purification, Xiaomi also recommends keeping doors and windows closed while the purifier is operating.

For a small bedroom or home office, I find the compact size particularly practical because the purifier is only about 35.5 cm tall and weighs around 2.2 kg. It is easy to move when you need to use it in another room.

3. How to Use the Xiaomi Air Purifier 4 Compact

Using the Xiaomi Air Purifier 4 Compact is mostly a matter of three controls: Power, Mode, and Light Adjustment.

• Press Power to turn the purifier on or off.
• Press Mode to cycle through the available operating modes.
• Press Light Adjustment to switch the display between on, dim, and off.

If Child Lock is enabled, the physical controls will not respond normally until the feature is disabled.

3.1. Understanding Auto, Sleep, and Manual Modes

The Xiaomi Air Purifier 4 Compact has three operating modes: Auto, Sleep, and Manual.

• Auto Mode automatically adjusts the operating mode according to indoor air quality. It is the simplest option if you want the purifier to manage its operation without manually changing the fan setting.
• Sleep Mode is designed for quieter nighttime operation. Xiaomi rates it at around 20 dB, and the display light can be turned off for a darker room.
• Manual Mode allows you to set and save the coverage area through the Xiaomi Home app, which the purifier uses to adjust its purification efficiency.

For everyday use, Auto Mode is the easiest place to start. Sleep Mode makes more sense at night, while Manual Mode is useful when you want more control through the app.

3.2. Xiaomi Air Purifier 4 Compact PM2.5 Color Indicator

The air-quality indicator uses four colors to show the detected PM2.5 level.

These values come directly from Xiaomi’s user manual. The indicator gives you a quick visual reference without requiring you to open the Xiaomi Home app.

One limitation is worth knowing: the Compact does not show a numerical PM2.5 value directly on the device. The color indicator is useful for spotting changes, but it should not be treated as a replacement for professional air-quality measurement equipment.

3.3. How to Enable Child Lock and Adjust Display Brightness

To enable or disable Child Lock, press and hold the Mode Switch button for 7 seconds. The Child Lock indicator shows whether the function is active. To adjust the display brightness, press the Light Adjustment button to cycle through:

• On
• Dim
• Off

Turning the display off is particularly useful at night if you want the purifier running without a bright indicator in the room.

4. How to Connect Xiaomi Air Purifier 4 Compact to Xiaomi Home App

The Xiaomi Air Purifier 4 Compact connects to the Xiaomi Home app using a 2.4 GHz Wi-Fi network. It does not support 5 GHz Wi-Fi. To connect the purifier:

1. Install the Xiaomi Home or Mi Home app on your phone.
2. Sign in to your Xiaomi account.
3. Turn on the Air Purifier 4 Compact.
4. Open the app and tap the + button.
5. Select the Xiaomi Air Purifier 4 Compact.
6. Follow the pairing instructions shown in the app.
7. Select your 2.4 GHz Wi-Fi network.
8. Enter your Wi-Fi password and complete the setup.

The app can be used to control the purifier, switch operating modes, monitor information, adjust settings, and use smart functions. The exact interface may change as Xiaomi updates the app.

4.1. How to Reset the Wi-Fi Connection

To reset the Xiaomi Air Purifier 4 Compact’s Wi-Fi connection, press and hold the Light Adjustment button for 7 seconds. The purifier will make a notification sound and the Wi-Fi indicator will blink when the reset is successful. After resetting the connection, open Xiaomi Home and pair the purifier again.

If the purifier still refuses to connect, check that your router is using 2.4 GHz Wi-Fi, your phone is connected to the correct network, and the purifier is within a reasonable range of the router. Xiaomi also recommends checking the Wi-Fi password and network condition before trying the reset again.

5. Care, Cleaning, and Filter Replacement Guide

The Xiaomi Air Purifier 4 Compact requires relatively simple maintenance, but the filter and particle sensor should not be ignored. Xiaomi recommends replacing the filter approximately every 6–12 months, depending on usage and conditions.

The compatible replacement filter is AFEP7TFM01. Xiaomi lists this filter specifically for the Xiaomi Air Purifier 4 Compact.

5.1. How to Clean the Filter Compartment and Particle Sensor

Turn off the purifier and unplug it before cleaning or performing maintenance. For the filter compartment and air inlets:

1. Remove visible dust and debris with a vacuum cleaner.
2. Wipe accessible surfaces with a soft, dry cloth.
3. Do not spray water directly onto the purifier.
4. Do not rinse the purifier or wipe it with a soaking-wet cloth.

Xiaomi also recommends regularly removing dust, hair, and other particles from the outer filter mesh and air inlets. For the particle sensor:

1. Turn off and unplug the purifier.
2. Open the particle sensor cover using a non-sharp tool.
3. Remove dust using an air blower or a hair dryer set to cool air.
4. Gently wipe dust from the sensor with a dry cotton swab.
5. Avoid using hot air.

Xiaomi recommends cleaning dust from the sensor approximately every six months.

5.2. How to Replace the Filter and Reset the Filter Lifespan

The filter should be replaced when it reaches the end of its usable life or when the filter exhaustion indicator appears. To replace it:

1. Turn off and unplug the purifier.
2. Open the filter compartment.
3. Remove the old filter.
4. Install a compatible AFEP7TFM01 filter.
5. Close the filter compartment securely.
6. Put the purifier into standby mode.
7. Press and hold the Power button for 7 seconds to reset the filter reminder.
8. A notification sound and a brief green air-quality indicator confirm the reset according to the current Xiaomi user manual.

There are regional versions of Xiaomi documentation that describe slightly different reset durations, so if the instructions supplied with your unit differ, follow the manual for your specific region and model.

Do not wash the filter with water. Once the filtration media reaches the end of its service life, replacing it is the appropriate solution.

6. Troubleshooting Common Xiaomi Air Purifier 4 Compact Issues

The Xiaomi Air Purifier 4 Compact is generally straightforward to operate, but a few problems can appear during everyday use. Some are caused by simple things such as a blocked air intake or an expired filter, while others involve Wi-Fi pairing or the particle sensor.

Before assuming that the purifier is faulty, check the symptoms first. The troubleshooting guide below follows a simple problem → possible cause → quick solution format to help you identify the issue and fix common problems without unnecessary steps.

Filter Exhaustion Indicator Is Blinking

Problem: The filter exhaustion indicator is blinking.

Cause: The purifier has detected that the filter has reached the end of its recommended service life.

Quick solution: Replace the filter with a compatible replacement, such as AFEP7TFM01, then reset the filter reminder.

Xiaomi Air Purifier 4 Compact Cannot Connect to Wi-Fi

Problem: The purifier cannot connect to Xiaomi Home.

Cause: The network may be using 5 GHz Wi-Fi, the signal may be weak, or the pairing information may need to be reset.

Quick solution: Make sure you are using a 2.4 GHz Wi-Fi network, then hold the Light Adjustment button for 7 seconds to reset the Wi-Fi connection. After the Wi-Fi indicator starts blinking, try pairing the purifier again.

Airflow Feels Weak

Problem: The purifier does not seem to move as much air as expected.

Cause: Dust around the air inlets or filter compartment can restrict airflow. Incorrect placement can also block the intake.

Quick solution: Check the air inlets, clean accessible dust, inspect the filter, and make sure there is at least 20 cm of clearance around the relevant air inlets.

Air Quality Indicator Seems Inaccurate

Problem: The PM2.5 indicator does not seem to match the surrounding conditions.

Cause: Dust around the particle sensor, water mist, cooking fumes, smoke, or poor placement can affect particle detection. Xiaomi specifically recommends checking and cleaning the sensor when readings appear inaccurate.

Quick solution: Clean the particle sensor, keep the purifier away from direct drafts and sources of mist or fumes, and allow the device to monitor the room again.

The Purifier Makes an Unusual Noise or Smells Strange

Problem: The purifier suddenly produces an unusual sound or odor.

Quick solution: Turn it off, unplug it, and inspect the device for obvious problems. Xiaomi advises stopping use if the purifier produces unusual sounds, bad odors, overheats, or the fan operates irregularly. If the problem continues, contact Xiaomi or the seller for service.

7. My Hands-On Review of the Xiaomi Air Purifier 4 Compact

Specifications explain what the purifier is designed to do. Living with it for almost two years gives me a different perspective.

I have used the Xiaomi Air Purifier 4 Compact long enough to see where its small size becomes an advantage and where its limitations matter. For me, the most important part is not whether the purifier has the biggest CADR or the most sensors. It is whether I can place it in the right room and keep using it consistently.

7.1. The Compact Design Is Actually Practical

The Xiaomi Air Purifier 4 Compact measures about 35.5 cm tall, has a diameter of 22 cm, and weighs around 2.2 kg. That makes it relatively easy to move between rooms.

That matters more than it sounds.

An air purifier takes up space continuously. A smaller unit is easier to fit beside a bed, on a suitable table, or in a home workspace without making the room feel crowded.

7.2. The PM2.5 Indicator Helps Me Notice Changes

I find the color indicator useful because I can see changes without opening the Xiaomi Home app.

It is not a professional air-quality monitor, and I would not treat the color as a laboratory measurement. But for everyday use, having a simple visual signal is convenient.

The four-color system also makes the device easier to understand for someone who does not want to constantly check numerical PM2.5 readings.

7.3. Sleep Mode Makes Sense for Nighttime Use

Sleep Mode is one of the features I use most at night.

Xiaomi rates the mode at around 20 dB, and the display can be turned off.

That combination makes the purifier easier to leave running while sleeping. You do not have to keep looking at the display, and the low-noise mode is designed specifically for nighttime use.

7.4. The Low Power Rating Helps for Long-Term Use

The Xiaomi Air Purifier 4 Compact has a maximum rated power of 27 W. Xiaomi’s product information also promotes the device as having relatively low power consumption.

If you calculate the theoretical maximum—27 W running continuously for 24 hours a day over 30 days—the consumption would be about 19.44 kWh per month.

That is a worst-case calculation, not a prediction of actual household usage. Auto Mode and lower operating speeds can result in different consumption.

For a device intended to run for long periods, though, the relatively low maximum power rating is reassuring.

7.5. What Stands Out After Almost Two Years?

The biggest lesson for me is that an air purifier is easy to judge incorrectly if you only look for an obvious before-and-after effect.

You can see dust after vacuuming. You can see a clean floor after mopping. An air purifier is different. Much of its work happens in the background.

After almost two years, I value the fact that the Compact is small enough to fit into my routine, simple enough to operate without much thought, and capable enough for the room size it is designed for.

That does not make it the right purifier for every room. Its 230 m³/h CADR and 16–27 m² effective coverage clearly put it in the smaller-room category.

Frequently Asked Questions About Xiaomi Air Purifier 4 Compact

If you are looking for a quick answer rather than the full setup guide, these are the most useful questions to check first. The answers focus on the settings, maintenance, connectivity, and specifications that tend to matter most during everyday use.

1. What room size is the Xiaomi Air Purifier 4 Compact suitable for?

The Xiaomi Air Purifier 4 Compact is designed for an effective coverage area of 16–27 m², with a Particle CADR of 230 m³/h. It is therefore better suited to bedrooms, home offices, and other relatively small rooms.

2. How do I reset the Xiaomi Air Purifier 4 Compact Wi-Fi?

Press and hold the Light Adjustment button for 7 seconds until the purifier makes a notification sound and the Wi-Fi indicator starts blinking. You can then reconnect the purifier through Xiaomi Home.

3. Does the Xiaomi Air Purifier 4 Compact support 5 GHz Wi-Fi?

No. The Xiaomi Air Purifier 4 Compact supports 2.4 GHz Wi-Fi and does not support 5 GHz networks.

4. What do the Xiaomi Air Purifier 4 Compact indicator colors mean?

Green indicates 1–35 μg/m³, yellow 36–75 μg/m³, orange 76–150 μg/m³, and red indicates levels above 150 μg/m³. These colors correspond to the PM2.5 readings used by the purifier.

5. How often should I replace the Xiaomi Air Purifier 4 Compact filter?

Xiaomi recommends replacing the filter approximately every 6–12 months. Actual timing depends on usage and indoor conditions, so the filter indicator and Xiaomi Home app are useful additional references.

6. What filter does the Xiaomi Air Purifier 4 Compact use?

The compatible replacement filter is AFEP7TFM01. Xiaomi lists this filter as compatible with the Xiaomi Air Purifier 4 Compact.

7. Can I wash the Xiaomi Air Purifier 4 Compact filter?

No. The filter should not be washed with water. Clean dust from the purifier’s accessible surfaces and air passages, then replace the filter when it reaches the end of its service life.

8. How do I reset the filter after replacing it?

With the purifier in standby mode, press and hold the Power button for 7 seconds. A notification sound and brief green air-quality indicator confirm the reset according to the current Xiaomi user manual.

9. Who Is the Xiaomi Air Purifier 4 Compact For?

The Xiaomi Air Purifier 4 Compact makes the most sense when you need an air purifier for a smaller room rather than an entire home. Its 230 m³/h CADR, 16–27 m² effective coverage, compact body, Xiaomi Home connectivity, and 20 dB Sleep Mode give it a clear use case.

After almost two years of use, I would not choose it simply because the specifications look good on paper. I would choose it if the room fits its capacity and I want a purifier that is small enough to become part of the daily routine.

The easiest decision is also the most practical one: measure the room first, check the filter cost and availability, then decide whether the Compact’s capacity is enough.

Conclusion

A good air purifier is not necessarily the one with the longest feature list. What matters more is whether it fits your room, your routine, and the way you actually live with it. The Xiaomi Air Purifier 4 Compact keeps that idea fairly simple: set it up correctly, keep the airflow clear, maintain the filter, and let it do its job in the background.

When you think about it, using an air purifier is less about seeing an immediate result and more about building a small habit that quietly runs every day. The Xiaomi Air Purifier 4 Compact Manual can help you get the setup and maintenance right, but the real value comes from using the device consistently and understanding its limits.

If you have been using the Xiaomi Air Purifier 4 Compact yourself, what has your experience been like so far? I’d be interested to hear whether it has made a noticeable difference in your daily routine.