Sick building syndrome and allergies caused by chemical substances, mold, and dust mites pose serious risks even in rental apartments. From viewing checklist items to ventilation and cleaning after move-in, we explain from an expert perspective.
Reviewed by: Nobuyuki MoriPresident, M-Assets Co., Ltd. / Licensed Real Estate Transaction Specialist (Miyagi #018212)
Sick building syndrome is a collective term for health problems caused by chemical substances (VOCs: volatile organic compounds) released from building materials, adhesives, paints, and other materials in homes, as well as biological contamination from mold, dust mites, and similar organisms. The main symptoms include eye, nasal, and throat irritation, headaches, fatigue, and dizziness, and severe cases can lead to chronic health problems.
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The Building Standards Law, amended in 2003, made it mandatory to restrict the use of building materials that release formaldehyde and to install 24-hour ventilation systems. However, older rental properties built before regulations were enforced may still use non-compliant building materials. Additionally, even in newly built or newly renovated properties, adhesives and paints used in construction may not have completely off-gassed.
Properties that meet the following conditions may have a relatively higher risk of sick building syndrome. Be sure to carefully check these during viewings.
Age of Construction and Renovation Status
Indoor Environment
Mold and Humidity Environment
You can check the air environment using the following methods during a property viewing.
Checking by Smell Check for odors immediately upon entering the room. A sharp, pungent smell or chemical-like odor may indicate the release of formaldehyde or other VOCs. If you notice any unusual smell, open a window and ventilate the space, then check whether the smell persists.
Checking 24-Hour Ventilation Check whether 24-hour ventilation openings (intake and exhaust vents) are installed on walls or ceilings and are functioning. You can verify operation by holding a piece of paper or your hand near the vents to feel for airflow. If vents are blocked or clogged with dirt, request that the management company clean or repair them.
Using VOC Measurement Devices In recent years, affordable VOC and formaldehyde measurement devices (around 3,000–10,000 yen) have become widely available. While professional testing requires consulting specialized firms, simple measurement devices can provide a rough guideline. Especially for people with sensitive constitutions or households with infants or elderly members, pre-move-in testing is worth considering.
In addition to chemical substances, dust mites and mold are major causes of housing-related allergies. Special care is needed for people with asthma, atopic dermatitis, or allergic rhinitis.
Dust Mite Growth Conditions and Prevention Dust mites rapidly multiply in environments with temperatures of 25–30°C and humidity of 60–80% or higher. They concentrate in tatami, carpets, bedding, stuffed animals, and similar materials.
Prevention strategies:
Mold Growth and Countermeasures Mold develops wherever organic matter (wood, paper, wallpaper, etc.) and moisture are present. Be particularly watchful of areas where moisture accumulates, such as inside closets and storage spaces, walls facing exterior walls, and areas around windows—not just bathrooms and powder rooms.
Prevention strategies:
If you experience headaches, fatigue, eye or nasal irritation, and similar symptoms after moving in, sick building syndrome may be the cause.
First, Prioritize Ventilation Keep 24-hour ventilation running at all times, and open windows for at least one hour of ventilation on sunny days. Since the release of chemical substances decreases over time, the risk is highest immediately after move-in, and many cases improve within a few months.
Indoor Air Quality Testing by Specialists If symptoms do not improve, request that a building and housing center or environmental testing company measure indoor air quality (formaldehyde, toluene, xylene, etc.). If measurements exceed guideline values established by the Ministry of Land, Infrastructure, Transport and Tourism, you will have grounds to request improvements from the management company.
Notification to Management Company and Landlord If it is confirmed that chemical substance release from building materials is the cause, you can demand action from the management company or landlord as a "non-conformity of contract" under the rental agreement. Gather measurement data and symptom records before negotiating.
Consulting a Doctor If symptoms suspected of being sick building syndrome persist, it is important to consult an environmental health specialist, dermatologist, ear-nose-throat specialist, or allergist and have them diagnose that the indoor environment is the cause. A medical certificate is useful for notifying the management company and filing insurance claims.
To ensure a healthy indoor environment, check the following during your property viewing:
Indoor air quality is a crucial factor for a healthy and comfortable rental living experience. Conduct thorough pre-move-in checks while considering your own and your family's physical characteristics as you select a property.
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