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The text provides a brief summary of the various applications of fieldbuses in the automotive industry (FA) and the chemical industry (PA). On this basis, in-depth discussions were held on the specific problems encountered in the application of fieldbuses in the chemical industry (PA). Finally, it is concluded that a remote I/O system with a bus interface that can be installed directly in hazardous areas (Zone 1) will be the product we need most in the coming years. If people are classified based on their attitude toward field buses, they can generally be divided into the following four categories: A, Users ； B. Firm supporters ； C. Complete opponents ； D. Those who have not yet made a decision. In the field of factory automation, or more precisely in the automotive industry, over 50% belong to category A, around 90% belong to category B, while the proportion of those in categories C and D is very small. In this field, the benefits brought by field buses are already very evident, so there is no need to discuss whether field buses should be used or not. However, the situation is quite different in the field of process automation. For example, in the chemical industry, the proportion of Group A individuals is very small ； The number of people in Category B is gradually increasing ； The proportion of Group C individuals exceeds 20% ； However, Group D still accounts for a very large proportion. In these two distinct industrial sectors, the actual use of field buses also shows significant differences. In the automotive industry, considerations are given to which type of bus to use (the parameters and structure of the bus are very important); for example, whether it should be PROFIBUS, INTERBUS, or DEVI-CENET, etc. Decisions are also made regarding whether to use copper wires, fiber optics, or a combination of both, as well as whether to employ a \"plug and play\" approach or connection terminals for linking the buses. The various existing and continuously evolving fieldbus products and solutions are fully capable of meeting users’ needs. The situation in the field of process automation is completely different. Despite having many supporters, in reality there are only a few test-oriented installation examples of PROFIBUS PA and FOUNDATION FIELDBUS; it seems that widespread use of fieldbuses still has a long way to go. Although perhaps 50% of people believe that using buses can reduce costs while increasing flexibility, determining which fieldbus system is suitable remains a significant challenge. Like other industrial sectors, the chemical, petrochemical, and pharmaceutical industries must take economic and commercial factors into account. Some of the special circumstances they face make it difficult for people to decide to use fieldbuses. Next, let’s analyze these special cases. In the chemical industry, there are two different processes: one is the so-called \"batch\" production process, and the other is the so-called \"continuous\" production process. In both of these processes, an unexpected stop midway can result in significant losses, as it takes several days to clean the reactors and pipelines. Therefore, the system’s ability to operate continuously is an issue that must be considered first, which also explains why \"fault safety\" is given such emphasis in system design within this field. In other words, if a fieldbus is used, the system’s continuous operation capability must not be lower than that of a system using a traditional control structure. In traditional control structures, a failure at a certain point only affects the operation of that one or a few related points, without impacting the entire control system. However, this concept of point-to-point connections (where only two points are connected by a single wire) is contradictory to the concept of fieldbuses, which aim to connect as many devices as possible onto a single bus cable. To achieve this, it is necessary to consider designing the fieldbus system as a redundant structure, but this reduces the potential for cost savings. At the same time, this raises another important issue: it requires that each field device have two bus interfaces or that a ring-shaped bus structure be used to connect the field devices, which is obviously uneconomical. If a certain number of small remote I/O units are used to connect the field devices, redundancy in the bus lines can be achieved by configuring two gateways on those remote I/O units. The greatest advantage is that **it reduces the number of connection components between the field instruments and the bus, thereby lowering wiring costs**. Another more complex issue is explosion protection at the site. Conventional explosion protection methods are quite simple; for example, the intrinsically safe (EX i) method, which prevents the generation of sparks by limiting energy, and the flameproof (EX d) and encapsulated (EX m) methods, which use special enclosures for protection, among others. However, these methods all conflict with the basic concepts of fieldbuses. If energy constraints are taken into account (by using the intrinsically safe approach), then the number of field devices that can be connected to each bus branch is reduced. For example, on each bus branch of PROFIBUS PA or FOUNDATION FIELDBUS, only 6–10 field devices can be connected; whereas without such energy restrictions, more than 100 field devices could be connected to a single PROFIBUS DP branch (using repeaters). If methods such as explosion protection (EX d) or encapsulation (EX m) are used (which are often combined with enhanced safety measures), there are basically no restrictions on the energy that can enter the hazardous area. However, the drawback of these two methods is that the power supply must be cut off before field equipment can be repaired or replaced. However, for fieldbus systems, the “hot plugging” of devices should be a basic requirement. Of course, a system approach can be adopted in which the bus is intrinsically safe, and the field devices use explosion-proof (EX d) or encapsulated (EX m) methods; in other words, the field devices all employ an independent power supply that does not rely on the bus for power, while the signal energy transmitted over the bus is kept at an intrinsically safe level. If this is done, a power cable must be laid alongside a communication cable. However, there are also significant difficulties in supplying power to each field device, as the supply voltage for most instruments is currently 24 volts DC; yet providing a remote power source at 24 volts DC is a challenging issue to resolve ； If 220V AC power is used, not only does the instrument need to be modified, but the use of 220V AC in hazardous areas also poses significant safety risks. Is there a better solution? In comparison, remote I/O seems to be the best option: it uses traditional installation methods for connecting field devices; a single power supply module is used to power multiple field devices (with redundant configuration possible if needed); field devices can be hot-plugged during maintenance or replacement; and it is more cost-effective. Summarizing the above points, we can see that the remote I/O approach offers more advantages over the current field bus solutions. However, remote I/O is not meant to replace field buses; it must be connected to the PLC or DCS via field buses. One of the main purposes of using remote I/O is to address the issue of the need for a unified bus interface for connecting field devices to the bus; configuring a bus interface for each field device, including those that transmit digital signals, is currently neither economical nor practical ； On the other hand, it is to address the explosion-proof issues at the site, allowing for both intrinsically safe explosion protection and live plugging and unplugging. Upon further analysis, we found that while remote I/O solves the problem of the need for a unified bus interface when field devices are connected to a bus, if it can be installed directly within the hazardous area – that is, if it functions not only as a device associated with an intrinsically safe device (which must be placed in a safe area) but can also be installed directly in the hazardous area using various explosion-proof methods – then a large number of wires and cables running from the hazardous area to the safe area can be easily eliminated. At this point, we can assert that such a remote I/O system with a bus interface, which can be installed directly in hazardous areas (Zone 1), will be one of the most needed systems in the coming years.