Heuristic Evaluation – Ninja Air Fryer

Last year, my fiancé bought a Ninja Air Fryer. Since then, we have used it only twice. Rather, I should say, she used it twice. I watched her do it, and roughly understand the steps to take to cook the food placed in it, but I haven’t bothered to use it. I am just more used to using a stove-top, oven or microwave, but I also find the air fryer to be confusing, complex, and hard to learn. On the other hand, I haven’t even bothered to try to learn it. I blame myself, but it is possible that there is something about the design that makes me feel this way, or at least does not mitigate my feelings.

“Two of the most important characteristics of good design are discoverability and understanding. Discoverability: Is it possible to even figure out what actions are possible and where and how to perform them? Understanding: What does it all mean? How is the product supposed to be used? What do all the different controls and settings mean?” (Norman, D., 2013, p.3, The Design of Everyday Things)

The air fryer is certainly a device that does a lot of things, and using it is achieved in very few steps, but it is not clear which steps to use, and how to go about doing them. It has very few buttons, and so has a great amount of discoverability, if only I would bring myself to use it one time and actually engage in that discovery. The simple functions of the device are not very difficult to understand, but it is hard to know which setting is the right one for the type of food I want to cook. In the amount of time it takes to figure it out, I could have already cooked the food using the devices I am used to using. One day, air fryer. One day.

Figure #1: Picture of a Ninja Air Fryer from the front, with slide in the open position, with a category of settings called “Air Fry/Stove Top.”

Figure #2: Picture of Ninja Air Fryer from side, with lid open, showing a coil with a fan behind it.

Figure #3: Picture of a Ninja Air Fryer from the front, with slide in the open-middle position, with a category of settings called “Steam/Crisp.”

Figure #4: Picture of a Ninja Air Fryer from the front, with slide in the closed-left position, with a category of settings called “Pressure.”

Conceptual Model

I think of my air fryer as a crock pot, pressure cooker, oven, and microwave. It is the first three of these, and not the fourth, but I find myself thinking of it as a microwave anyways. It is all these things and more. I don’t even know how much more because I’ve not seen any but the simplest functions of it used (the air fryer setting; one of 15 different settings).

“Mental models, as the name implies, are the conceptual models in people’s minds that represent their understanding of how things work…a single person might have multiple models of the same item, each dealing with a different aspect of its operation: the models can even be in conflict.” (Norman, D., 2013)

When the device operates on Air Fryer/Stovetop mode I believe there is a coil under the pot which heats up the pot the way a stovetop heats a pot, from the bottom. I believe the fan above moves the heat around, while the coil at the top may or may not be active.

When the device operates on Steam/Crisp mode, I believe the bottom burner is off and the top burner is on, with the fan moving the heat around from above. Perhaps the coil above reaches a higher temperature, but perhaps not.

When the device operates on Pressure mode, the fan must not be active, because air cannot escape the device. I assume that both the top and bottom coil would be active, and as the air within the device is heated the pressure in the device increases, and is released in small amounts when it goes past a certain pressure level.

The fact that I am so unsure about the way each mode works demonstrates the complexity of this device, and lends to the lack of understanding I have about its use. In a way, the device is not the same as any of my conceptual models but is perhaps a hybrid mix of two or more of them and may even include elements of a conceptual model I have not yet conceived of!


Don Norman (2013) defines an affordance as “a relationship between the properties of an object and the capabilities of the agent that determines just how the object could possibly be used” (p.11).

The air fryer affords me heating and cooking of food. I must be cooking a lot of one thing to use this product, but it is unclear how much is too much. There is a pot within the device, and there is an insert that fits into the pot, which allows air to go around and underneath it.

Figure #5: Picture of a Ninja Air Fryer from above, with lid opened, revealing the insert within the pot.

This insert affords me the ability to place many pounds of chicken wings, but it is unclear if they would cook properly if there were more than a single layer of wings. The pot without the insert affords me the ability to hold a large volume of liquid, but there is no line to indicate the level which is the fullest it can safely or effectively operate at.


This device has some constraints. It won’t start operating until I select a setting and hit the start button. If I fail to adjust the temperature and time from the default, the defaults are automatically applied. It won’t let me use the pressure setting, unless the slide is to the left, which closes the air vents so that pressure will build up. It will, however, let me use the pressure setting without closing the manually adjusted vent at the top of the lid.

“Physical constraints are made more effective and useful if they are easy to see and interpret, for then the set of actions is restricted before anything has been done. Otherwise, a physical constraint prevents a wrong action from succeeding only after it has been tried.” (Norman, D., 2013. p.125)

I cannot identify any cultural constraints for this item. All cultures on earth, except for a few tribes that have never experienced contact with the outside world, have access to electricity and modern methods of cooking.

Norman defines semantic constraints as “those that rely upon the meaning of the situation to control the set of possible actions” (p.129). Due to my understanding of the use of the device for cooking food, I would constrain myself from heating things in it other than food.

“Natural mappings,” Norman writes, “work by providing logical constraints…there is a logical relationship between the spatial or functional layout of components and the things that they affect or are affected by” (p.130). Because of the minimal number of ways to interact with this device, being three buttons, one circular, central knob, one slide and one pressure knob atop the lid, there is a logical constraint to the way that this device can be used.


Norman (2013) defines feedback as “communicating the results of an action” (p.23). This air fryer beeps when you press a button, and when you turn the knob. It makes an alarming, but not too unpleasant, sound when it is done. When it starts cooking, it makes an audible sound, and the timer begins counting down. When the “Keep Warm” button is pressed before any cooking has been started or finished, no sound is made, and no sound comes from the device to indicate an operation has commenced. This leaves a person to assume that nothing has happened.


Norman (2013) defines mapping as “the relationship between the elements of two sets of things” (p.20). The buttons on this device are to the right and the left of the central, circular knob, and below the display. This seems logical, but has no real meaning other than that it fits within the frame of a rectangular display, and can be seen fully from the front without having to rotate the device or to move around it. The circular, central knob turns clockwise to cycle down and to the right on the list of settings. It turns counterclockwise to cycle up and to the left on the list of settings.

Overall Assessment

Norman (2013) points out: “Many products defy understanding simply because they have too many functions and controls” (p.3). This air fryer certainly qualifies as a product that defies understanding for the fact that it has so many functions. It doesn’t have too many controls. The mapping is natural enough, but not familiar. The feedback is sufficient, but understanding of the device is not assisted by it. The product has a proper amount of constraints facilitated by the simplicity of the design and the minimal amount of parts. It affords the exact ability to do what it is intended to do, which matches what it is desired to do. My only complaint about the device is that it is difficult to want to learn to use. It is not difficult to use, but requires some time spent looking at the instruction manual before it becomes familiar, and even then only one of the 15 settings will be remembered. The rest will remain a mystery, even if they are similar enough and not difficult. Because of the availability of products that I’m more familiar with, I tend to not use my air fryer, but if I didn’t have a stove or a microwave I’d be able to use it to heat and cook everything I eat, whether it be raw meat, soup from scratch, or leftover meals. My air fryer is extremely useful.

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