Introduction

The study started from a problem in which it is detected that the signage within the work area is deficient therefore this distorts the preventive messages that are wanted to be made known to those who make use of the machinery, to avoid incidents and accidents during the performance of the aforementioned activity. Therefore, the study realized contributes critically to the productivity and safety of people who carry out manufacturing activities such as machining parts.

Because of a relevant factor within companies is the adequate is the adequate management of safety and health systems, this is reflected significantly in the reduction of accidents and occupational diseases, influencing the attitudes and behavior of employees in a positive way (^{Vinodkumar & Bhasi, 2010}). There are risk factors to which employees are exposed when developing work activities, these risks can cause accidents, therefore, disabilities can be generated and as a result, effective hours of work are lost (^{Nag & Patel, 1998}). One of the most important consequences for business administration are the economic losses caused by occupational accidents derived from low productivity (^{Shalini, 2009}). Among the most important operational controls, it is considered to implement adequate management to eliminate, replace or reduce the likelihood of risk, to which workers are exposed, studies show that investing in safety is reflected in a positive way in reducing accidents, better worker performance, increase in productivity and quality of manufactured products or services provided. (^{Shirali et al., 2018}).

The implementation of a security management system is an operational control to be used with the use of security signs and symbols. Which are a system that provides information on safety and hygiene, consist of a geometric shape, a security color, a contrasting color and a symbol (^{Secretaría del Trabajo y Previsión Social, 2008}). It is considered that, for the use of safety signals, the worker must know and be familiar with this type of information for an adequate understand the warning or message that is being transmitted and then avoid accidents.

Worldwide there are organizations that contribute to standardize the application of signals in the industrial sector within which are ISO and ANSI (^{Davoudian & Azari, 2017}). These signs are effective as long as they are designed in compliance with ergonomic principles, human factors, and cognitive features. (^{Moradi et al., 2014}). In addition, they provide interaction between the human being and the environment, it is a method of control and prevention of the most used (^{Davoudian et al., 2015}). The International Organization for Standardization (ISO) has a Technical Committee (ISO TC 145) that addresses the problems of standardization in the field of graphic symbols, establishing principles for the preparation, coordination and application of graphic symbols (Neves et al., 2018). Within the standards are the following: ISO 3864 - Graphical Symbols Package, ISO 3864-1: 2011-Graphical symbols - Safety colors and safety signs - Part 1: Design principles for safety signs and safety markings, ISO 3864-2: 2016 -Graphical symbols - Safety colours and safety signs - Part 2: Design principles for product safety labels, ISO 3864-3: 2012 Graphical symbols - Safety colours and safety signs - Part 3: Design principles for graphical symbols for use in safety signs and ISO 17398: 2004- Safety colours and safety signs - Classification, performance and durability of safety signs.

The American National Standards Institute (ANSI) provides up to date information and guidance on safety signals, focused on the transmission and visual understanding of information so that people can distinguish between safety signals, labels or other information that they want to transmit by visual message. The standards proposed by ANSI are mentioned below: ANSI / NEMA Z535 SET-Safety color code, ANSI Z535.1-2017-Safety Colors, ANSI Z535.2-2011 (R2017) -Environmental and Facility Safety Signs, ANSI Z535. 3-2011 (R2017) Criteria for Safety Symbols, ANSI Z535.4-2011 (R2017) Product Safety Signs and Labels, ANSI Z535.5-2011 (R2017) Safety Tags and Barricade Tapes (for Temporary Hazards), ANSI Z535.6 -2011 (R2017) Product Safety Information in Product Manuals, Instructions and Other Collateral Materials, ISO 3864-4: 2011-Graphical symbols - Safety colours and safety signs - Part 4: Colorimetric and photometric properties of safety sign materials (^{American National Standards Institute, 2018}). In Mexico there are regulations that help rule the implementation of safety and health signals in work centers, the government entity faculted for inspections of the aforementioned is the STPS (Secretaría del Trabajo y Previsión Social), which issues the following standards: NOM-018-STPS-2000-System for the identification and communication of hazards and risks by hazardous chemical substances in a workplace (^{Secretaría del Trabajo y Previsión Social, 2000}) and NOM-026-STPS- 2008- Colors and signs of safety and hygiene, and identification of risks by fluids driven in pipes (^{Secretaría del Trabajo y Previsión Social, 2008}).

Application and contributions for security signals are described below; the first study is applied to Italian users on the understanding or interpretation of safety graphics used in agricultural machinery, in which the need for training courses that focus on safety graphics and their meanings is discussed, as well as the need for improving the graphics to make them easily understandable (^{Caffaro et al., 2017}).

In another investigation, the understanding of Chinese and Korean citizens about the security symbols of the United States are assessed, and how successfully they could interpret the meaning of them, the assigned ratings are related to how adequately the symbols transmit the message, how Appropriate is the design of each of these, the results of this study underscore the importance of developing safety symbols with end users in mind and within the results should be provided useful information to assist in the design of easier safety symbols to use (^{Chan et al., 2009}).

In addition, a study was conducted that measured how people say they interpret hazard levels associated with signal words and colors in a laboratory situation. However, the only really strong finding is that of all the combinations tested DANGER on a red background is associated with the greatest amount of hazard. Perceptions about the levels of hazard represented by CAUTION and WARNING are much less consistent. Some people associate CAUTION with the least amount of hazard, others think WARNING occupies that position and, on the average, people perceive CAUTION and WARNING as closer to each other than either is to DANGER, (^{Chapanis, 1994}; ^{Chan & Courtney, 2001}).

Finally, it is important to mention, in order for warnings to be effective, they must accomplish two objectives: they must be noticed and encoded; and they must provide understandable information needed for recipients to make informed decisions regarding compliance. A number of variables or factors have emerged as being especially significant in determining whether or not a warning achieves these objectives. These factors include both warning system design variables as well as characteristics of the target audience and the situation in which the warning is presented. (^{Laughery, 2006}).

Methods

The safety signals contribute to improve working conditions, within a manufacturing laboratory it is intended to detect operational controls to improve productivity and avoid accidents during the development of activities with the use of machinery. Therefore, in order to carry out a diagnostic on safety signage in this workplace, it is necessary to use a comparison standardized to carry out such evaluation, in Mexico the regulations issued are the NOM-026-STPS, which is responsible for establishing the requirements in terms of colors and signs of safety and hygiene and the identification of risks by fluids driven in pipes. According with this study is carried out in which a diagnostic is developed of compliance with the 026 standard on the correct use of safety signals, which is applied in the following order:

1. Recognition of the place: The workplace is identified according its dimensions, the machinery that is used and the risks involved with the use in this are known:

By using AutoCAD software, the technical drawing of the 2D workplace is represented, which contains the following measures:

Figure 1 shows the measurements of the manufacturing laboratory plan and the distribution of the work team, based on these measurements was located the midpoint or geometric center of the work area, to calculate the distances of location of the signage, as well as the width and height measurements of each one of the safety signs and symbols that are required in this laboratory.

The workplace is divided in two; A and B, each with its respective geometric center, as shown in Figure 2 and Figure 3, to later perform the calculations applying the NOM-026-STPS standard. In Figure 2 it can be seen that the work area (A) is divided into different sections that form a triangle where it is necessary to calculate the distances c, which is the distance at which the signal will be located from the geometric center, this is necessary to calculate of base and height dimensions.

The distance c, is calculated from (1) known as the Pythagorean theorem:

From this equation the distance c = L for its substitution in the equations that will be applied based on the norm.

In the manufacturing laboratory should be located signals in case of fire, as: fire extinguisher and hydrant. However, only extinguishers are detected in the work area which do not comply with the permissible distance established by NOM-002-STPS, which mentions that fire extinguishers must be at least 23 m away from each other. The proposed distribution is shown in Figure 4 with the distance between them is:

The extinguisher 1 is at a distance of 23 m from the extinguisher 2, the extinguisher 2 is at a distance of 23 m from the extinguisher 3 and finally the extinguisher 3 is located at a distance of 16.3 m from the extinguisher 1.

2. The machinery that is inside the workplace:

As the NOM-026-STPS mentions, a safety symbol can be drawn up in case the standard does not present it in its appendices, it must have the written indication and its associated image, therefore, in the risks associated with the use of the machinery a suggestion of this safety signal is not presented and this will be proposed according to another standard that can supply with this need. In addition, these signals must have a triangular geometric shape, a yellow background, a contour band and a black symbol (See Table 1).

3. Guarantee that the application of color, signaling and identification of the pipeline are subject to maintenance that ensures visibility and readability at all times:

A checklist was made to detect if the safety signs are visible and if they are receiving maintenance, which is shown below according to Table 2:

4. Locate the existence of safety signals in the workplace:

The following checklist was made to identify which safety signals are missing and which are incorrect (See Table 3):

5. The identification of the pipeline in workplace according Table 4:

6. Finally, the proposal of the missing safety signals and the one that is incorrect or deficient according to the standard of the standard must be made:

The equations for calculating the size of the safety signal are mentioned below:

The safety signals of Emergency facilities should be Square or rectangle. The relation of sides will be at most 1: 2. Using the following equations

The safety signals of Risks or hazards should be Equilateral triangle; the base should be parallel to the horizontal. Using the equations 2 and 5

The safety signals Mandatory action should be circle. Using the following equations

The safety signals of prohibition should be circle with circular band and diagonal oblique band at 45 °, with the horizontal arranged from the upper left to the lower right. Using the equations 6

The safety signals in case of fire should be Square or rectangle. The relation of sides will be at most 1: 2. Using the equations 2 and 4

The formula for calculating the signage is applied as shown below:

Based on the area of Figure 2, the triangle with points a, b, c is taken; the distance c is calculated from the geometric center to the place where the signal will be located, where a = 4.25 m and b = 4 m. Using Eq. (1), it has

For a signal of rectangular shape, the relation of the dimensions must be 1: 2, the base will be twice the height, the height is calculated as follows

The base is obtained to find b from the following equation

Below is the calculated measurements for each of the safety signals according to the application of the NOM-026-STPS (See Table 5).

Discussion and analysis of results

Conclusions

The study previously conducted arose from the need to correct the safety signals that was placed in a Manufacturing Laboratory, the personnel who placed existing safety signals are unaware of the regulatory compliance for the correct placement of these in Mexico. It is worth mentioning that the results and analysis are totally attached to the compliance requested by the NOM-026-STPS, therefore, the interpretation and proposals are based on following up on the regulatory obligations acquired by the organizations in the Country.

A diagnosis was made of the regulatory compliance with the NOM-026-STPS about signs of emergency installations, risks or hazards, mandatory action and prohibition. We detected great opportunities for change that are proposed in the development of this article to improve the work environment avoiding accidents and occupational diseases, resulting in improved productivity.

Among the most important findings is the safety signals deficiency on: emergency facilities, risks or dangers and prohibition.

It is important to mention that the distribution of the machinery is not the most appropriate according to its use, since the spaces are very small to delimit corridors and there is obstruction of the emergency exit for this should be important before its accommodation use of the method (Systematic Layout Planning). However, in this study the design and rearrangement of machinery and equipment is not within the scope.

There is obstructed signage in the work area and maintenance is not provided on the colors and visibility of the same. There is electrical piping next to the eyewash, which represents an electrical risk. There is also hydraulic pipe (compressor) next to pipes or electrical installations, this represents a risk of fire in the event of a short circuit.

Finally, it is concluded that the signage does not comply with the specifications according to the Mexican regulations, no standard for the identification of the pipeline is applied. But it is important to highlight that corrective measures are proposed that will change the conditions and above all avoid sanctions by Civil Protection or the Secretaría del Trabajo y Previsión Social in a future audit on the compliance of the same without leaving aside integrity of those who work within this area of work.