An EOQ Model for Non-Instantaneous Deteriorating Items under Pandemic Conditions using Triangular Intuitionistic Fuzzy Numbers SAHEDEV 1 , YOGENDRA KUMAR RAJORIA 2 , ANUBHAV PRATAP SINGH 1 , NISTHA KUMARI 3 , PRAWAR 2,* , ANJALI NAITHANI 4 1 Department of Mathematics, Shri Guru Ram Rai (P.G.) College, Dehradun, Uttarakhand, 248001, INDIA 2 Department of Mathematics, School of Basic and Applied Science, K.R Mangalam University, Gurugram Haryana, 122103, INDIA 3 Department of Mathematics, Graphic Era Deemed to be University, Dehradun, Uttarakhand, 248001, INDIA 4 Amity Institute of Applied Sciences, Amity University, Uttar Pradesh, 201303, INDIA Abstract: - The COVID-19 pandemic has significantly disrupted global business operations, causing challenges in supply chain management, particularly for perishable and deteriorating items. This study develops an Economic Order Quantity (EOQ) model for non-instantaneous deteriorating products, where demand is dependent on selling price. The model incorporates deterioration costs and salvage value, providing a realistic framework for inventory management during uncertain conditions. To handle uncertainty, triangular intuitionistic fuzzy numbers (TIFNs) is implemented and for defuzzification the centroid method is used. A numerical example validates the model, and sensitivity analysis demonstrates its robustness across various parameters. This model offers valuable insights for optimizing order quantity and minimizing total costs in the context of pandemic-induced disruptions. The primary objective is to optimize overall costs and determine an optimal cycle, order quantity under fuzzy environment. Key-Words: - Deterioration, selling price dependent demand, EOQ model, covid-19 pandemic, salvage value, Triangular intuitionistic fuzzy number (TIFNs). Received: March 2, 2025. Revised: July 7, 2025. Accepted: August 3, 2025. Published: Septemebr 19, 2025. 1 Introduction The coronavirus was a communicable disease that mostly affected the respiratory system in people. COVID-19 stands for “Novel Corona Virus Disease 2019”. The first discovery of this virus in Wuhan, China in 2019 led to its rapid global spread. The World Health Organization proclaimed it a worldwide epidemic in March 2019 after it had spread to so many countries. A painful throat, tight muscles, fatigue, and loss of taste and smell were among the symptoms that people with this disease encountered. This dangerous sickness, which was growing stronger by the day, claimed the lives of a significant number of individuals. Business had suffered greatly because of the epidemic. One of the biggest peacetime problems facing business and government in the last century was COVID-19. During the lockdown and shutdown phases, the market was the only one that was open five days a week, with relatively limited daily hours. Also, out of concern for security, the government fortifies the borders of a number of cities. On both the supply and demand sides, pandemic has an impact on the supply chain. Obtaining supplies of resources and WSEAS TRANSACTIONS on BIOLOGY and BIOMEDICINE DOI: 10.37394/23208.2025.22.41 Sahedev, Yogendra Kumar Rajoria, Anubhav Pratap Singh, Nistha Kumari, Prawar, Anjali Naithani E-ISSN: 2224-2902 438 Volume 22, 2025