Introduction:
Factories are industrial establishments where goods are produced or manufactured. They play a crucial role in the economy by providing employment opportunities and producing goods for consumption. There are several components that are typically found in factories, but out of the given options, the one that is always present is workers.

Explanation:
1. Chimney:
Chimneys are structures used for venting out smoke, gases, and other byproducts of the manufacturing process. While chimneys are commonly found in factories to ensure proper ventilation and environmental safety, not all factories have chimneys. Some factories may have advanced ventilation systems or may not require chimneys based on the nature of their production processes. Therefore, the presence of a chimney is not always guaranteed in factories.

2. Workers:
Workers are the most essential component of any factory. They are responsible for operating machinery, assembling products, managing logistics, maintaining equipment, and performing various other tasks required for the production process. Without workers, factories cannot function effectively or efficiently. Workers are the backbone of the manufacturing industry and are always present in factories.

3. Electricity:
Electricity is undoubtedly a vital requirement for factories as it powers the machinery, lighting, and other electrical systems. However, while electricity is commonly found in factories, its availability may vary depending on the location, infrastructure, and energy sources. In some cases, factories may have alternate power sources such as generators or may rely on other forms of energy like steam. Therefore, although electricity is prevalent in most factories, it may not always be present in the same form or to the same extent.

4. Sellers:
Sellers or sales personnel are individuals responsible for marketing and selling the products manufactured in factories. While factories produce goods for sale, the presence of sellers within the factory premises is not mandatory. Sales activities typically occur in separate locations such as showrooms, offices, or retail outlets. Therefore, sellers are not always found in factories.

Conclusion:
Out of the given options, workers are the component that is always found in factories. While chimneys, electricity, and sellers may or may not be present in factories depending on various factors, workers are an indispensable part of the manufacturing process and are essential for the functioning of any factory.