To design great products, you need to understand the value of round edges, one-handed operation, and impact resistance. Smaller products are more portable but more easy to lose. Metal is durable but cold to touch. Nuts and bolts can come loose with vibration so critical joints need to be locked in place with adhesive or pins.
Safe products protect users and the surrounding system. Generally, safe products fail less often and fail less harmfully. For a complete perspective, you must not only consider the normal operation of the product but also follow its total lifecycle and edge cases.
Look at the product's production, transportation, distribution, installation, maintenance, decommissioning, and recycling. For example, gravel rocks are safe on the ground of a construction site. Yet they can be dangerous while transported on unprotected trucks moving at high speeds. Loose rocks can crack the windshields of cars driving behind the trucks or worse. This is why modern freight trucks are either fully enclosed or covered by tarps to prevent the loose ejection of risky cargo across bumps on the road.
Fiberglass is a popular, cost-effective material for home insulation. Fiberglass is safe and effective once it is installed and fully enclosed. However, it is a serious danger to skin, eyes, and lungs while the insulation is ever exposed, such as during production, installation, and renovation.
Look at the spectrum of contextually probable situations that users and bystanders may experience. Consider a war-torn or earthquake-prone region in which recovery efforts save people from demolished homes. If the recovery workers do not address the dangers at the wreckage (by wearing even basic respirators), they may end up inhaling fiberglass particles that inflict long-term damage to their lungs. The same applies to firefighters who must protect themselves from toxic fumes emitted by certain products inside a burning building.
If you want to be a deep safety expert, you have to start simulating weird situations and understand everything that matters. Consider a child at a playground who is running away from a rabid animal. The design of the playground structure suddenly becomes a serious life-or-death factor. The child must either get somewhere that the animal cannot, or be able to navigate the structure more easily to evade the animal for long enough until adults arrive with help.
If a product has dangerous elements, people will tumble through primary and secondary barriers either accidentally or with other reasons in mind. Safe designs must make things truly difficult for people to hurt themselves with unintentionally. If a product has sharp corners and thin/burred edges, people will literally find it a pain to use. Even if the edges are inside the product, some edge case people will cut themselves on it. If a product is heavy, people will get hurt when they accidentally drop it on their feet. If a product is flammable, people will risk a fire when they accidentally keep it near a space heater.
Products should send warning signals or have planned failure points that trigger before reaching catastrophic failure. Fire alarms beep on low battery because the residents may suffer the tragedy of an undetected fire if the battery does not get replaced immediately. The inconvenience of a loud beep is far more tolerable when compared to its catastrophic alternatives.
Products should sacrifice themselves to protect the user. Modern cars have scrunch zones built into their front side that weakens the strength of the frame but softens the impact of a crash for the driver and passengers. Thus a car is more likely to be rendered inoperable from an accident, but its people more likely to remain safe.
Reliable products continue to work after prolonged use in extreme applications. Reliable designs use simple mechanisms with long-lasting materials. Designs with particularly complex or vulnerable mechanisms employ protective measures such as plastic encapsulation for integrated circuits and split pins for industrial bolts.
Durable products resist breaking under extreme environmental conditions. Durable designs avoid or strengthen all weak points, such as upgrading plastic parts to metal ones. Some notable durability considerations include galvanic corrosion between dissimilar metals, seals exposed to harsh conditions, and vibrational effects on machine joints.
Convenient products are easy to use, hard to lose, and readily accessible in times of need. Aesthetically intuitive designs help first-time and returning users operate the product safely and reliably. One-piece and unified designs prevent the separation and loss of functional parts, such as with cars connected by straps to their gas caps. Low maintenance designs help the user keep the product in likely working condition.
Affordable products are inexpensive enough for the average customer in the market. Price barriers determine whether a target demographic can justify buying a product of even outstanding quality. A notable price barrier separates the market for individuals from the market for businesses. Fundamental innovations and design tradeoffs improve cost factors most effectively; consider the economical production of membrane keyboards, which are less performant yet markedly cheaper than their mechanical counterparts.
Versatile products solve problems in a variety of applications. Good versatile designs seek to mirror the reliability of its single-use substitutes as much as possible, sacrificing price and ease of maintenance instead.
Small products save space and fit in more places. Even when the product's function requires a large size, such as with a large dinner table, consider how to reduce the size of non-functional components, such as the table legs. Consumer products must be small enough to fit through a typical doorframe. Industrial products should be small enough to fit within a typical cargo trailer or box truck.
Light-weight products are easier to lift, hold, and operate. Light products are more practical to carry in pockets and backpacks; more safe to store in high and sloped locations. Light designs are more compatible as a module of a larger system. For instance, a camera-on-tripod assembly is easier to move across a filming site if the camera itself is light to start with; a robotic arm with a light end-effector has a higher maximum payload.
Quiet products can be used continuously without causing a distraction. Quiet designs are particularly important for applications requiring close human presence, such as with residential appliances. Other times, noise reduction is necessary for sensors to detect signals from a relevant source, such as with an airplane air leak.
Tested products have run through simulations and real use experiences to pass all pre-defined requirements and common-sense expectations. Detailed tests bring confidence that reality will and does actually conform to the intentions of the design.
Active storage is storage without losing access convenience. It's different from archival storage in that the items must remain in a usable position, whether it's for personal or business use. You wouldn't store your keychain in a plastic bag in a box underneath your bed crowded with other boxes. It's just plain inconvenient to take it out and store it there again every time. So instead, when people come home they usually set their keys on a table; maybe placed on a wall-hanger, basket, or simple drawer.