According to the CDC WeChat official account, the weather is getting colder and colder. While keeping warm, windows should still be properly opened for ventilation. As the saying goes, 'flowing water does not rot, and the axis of the house does not become tangled.' Indoor air also needs to flow in order to maintain freshness. The function of opening windows for ventilation is that windows are important new air vents. Firstly, opening windows appropriately can dilute indoor pollutants through gas exchange. If not ventilated in a timely manner, harmful substances such as cooking fumes, coal smoke, and formaldehyde released from building materials can remain indoors for a long time, which not only stimulates the respiratory tract but may also affect lung function, blood pressure, and blood sugar levels; Coal smoke may even cause carbon monoxide poisoning, endangering life. Secondly, opening windows for ventilation can not only reduce indoor air pollution, but also help reduce odors such as carbon dioxide and sweat produced by human metabolism. The concentration of carbon dioxide is a key indicator for evaluating indoor air quality, and an increase in its concentration can stimulate the secretion of odor substances by the human body. When the concentration of carbon dioxide exceeds 0.1%, it may cause dizziness, headache, and lack of concentration, and it is also one of the important causes of "sick building syndrome". Thirdly, opening windows for ventilation can also reduce the pathogenic risk of indoor microorganisms. Ventilation is an important measure to reduce the spread of various pathogenic microorganisms. Winter is a peak season for influenza, and opening windows appropriately can dilute indoor virus concentration and reduce the risk of human to human transmission. In addition, ventilation can prevent clothing and food from getting moldy, which is a simple method for controlling mold. Fungi, as allergens, may cause eczema and asthma; The aflatoxin produced after grain mold growth also has certain carcinogenicity. How to achieve effective ventilation? So, what constitutes effective ventilation? Is it enough to only open doors and windows for a short time every day? The purpose of ventilation is to promote indoor air flow and replace indoor polluted air with fresh outdoor air. In the professional field, carbon dioxide concentration is often used as a standard to judge ventilation effectiveness. The Indoor Air Quality Standard (GB/T 18883-2022) recommends that the average concentration of indoor carbon dioxide should not exceed 0.1% in any one hour. Generally, households and offices lack professional monitoring equipment, making it difficult to directly determine ventilation conditions based on carbon dioxide concentration. However, as mentioned earlier, the concentration of carbon dioxide is closely related to indoor odors, so the ventilation effect can be roughly judged by odor: when entering the home from outside, if there is no obvious pungent odor or stuffiness, and the indoor and outdoor air feels equally fresh, it indicates good ventilation. Another issue with other ventilation methods is whether ventilation can be achieved without opening windows? The answer is affirmative. The fresh air system of central air conditioning is a ventilation method, but it is costly and may cause secondary pollution if used or maintained improperly. In addition to the fresh air system, general residential or small public places can install induced draft fans on chimneys or use non powered hoods to improve ventilation. However, it should be noted that regardless of the ventilation method used, it is advisable to avoid ventilation during heavy pollution periods as much as possible on hazy days. (New Society)