diff --git a/.chronus/changes/checkAvailableTypeName-2024-10-7-15-22-31.md b/.chronus/changes/checkAvailableTypeName-2024-10-7-15-22-31.md
new file mode 100644
index 00000000000..ca3ef477717
--- /dev/null
+++ b/.chronus/changes/checkAvailableTypeName-2024-10-7-15-22-31.md
@@ -0,0 +1,7 @@
+---
+changeKind: fix
+packages:
+  - "@typespec/openapi3"
+---
+
+Illegal characters in component keys
diff --git a/packages/openapi3/src/lib.ts b/packages/openapi3/src/lib.ts
index b8a8c9e0bcc..bd994c9a85c 100644
--- a/packages/openapi3/src/lib.ts
+++ b/packages/openapi3/src/lib.ts
@@ -275,6 +275,12 @@ export const libDef = {
         default: paramMessage`XML \`@unwrapped\` can only used on array properties or primitive ones in the OpenAPI 3 emitter, Property '${"name"}' will be ignored.`,
       },
     },
+    "invalid-component-fixed-field-key": {
+      severity: "error",
+      messages: {
+        default: paramMessage`Invalid key '${"value"}' used in a fixed field of the Component object. Only alphanumerics, dot (.), hyphen (-), and underscore (_) characters are allowed in keys.`,
+      },
+    },
   },
   emitter: {
     options: EmitterOptionsSchema as JSONSchemaType<OpenAPI3EmitterOptions>,
diff --git a/packages/openapi3/src/openapi.ts b/packages/openapi3/src/openapi.ts
index 6659ccdb194..fa533c0e0c1 100644
--- a/packages/openapi3/src/openapi.ts
+++ b/packages/openapi3/src/openapi.ts
@@ -1540,6 +1540,21 @@ function createOAPIEmitter(
     }
   }
 
+  function validateComponentFixedFieldKey(type: Type, name: string) {
+    const pattern = /^[a-zA-Z0-9.\-_]+$/;
+    if (!pattern.test(name)) {
+      program.reportDiagnostic(
+        createDiagnostic({
+          code: "invalid-component-fixed-field-key",
+          format: {
+            value: name,
+          },
+          target: type,
+        }),
+      );
+    }
+  }
+
   function emitParameters() {
     for (const [property, param] of params) {
       const key = getParameterKey(
@@ -1549,6 +1564,7 @@ function createOAPIEmitter(
         root.components!.parameters!,
         typeNameOptions,
       );
+      validateComponentFixedFieldKey(property, key);
 
       root.components!.parameters![key] = { ...param };
       for (const key of Object.keys(param)) {
@@ -1573,6 +1589,8 @@ function createOAPIEmitter(
       const schemas = root.components!.schemas!;
       const declarations = files[0].globalScope.declarations;
       for (const declaration of declarations) {
+        validateComponentFixedFieldKey(serviceNamespace, declaration.name);
+
         schemas[declaration.name] = declaration.value as any;
       }
     }
diff --git a/packages/openapi3/test/models.test.ts b/packages/openapi3/test/models.test.ts
index 70c198105fe..774c7deec96 100644
--- a/packages/openapi3/test/models.test.ts
+++ b/packages/openapi3/test/models.test.ts
@@ -102,6 +102,60 @@ describe("openapi3: models", () => {
     ]);
   });
 
+  describe("errors on invalid model names", () => {
+    const symbols = [
+      "!",
+      "@",
+      "#",
+      "$",
+      "%",
+      "^",
+      "&",
+      "*",
+      "(",
+      ")",
+      "=",
+      "+",
+      "[",
+      "]",
+      "{",
+      "}",
+      "|",
+      ";",
+      ":",
+      "<",
+      ">",
+      ",",
+      "/",
+      "?",
+      "~",
+    ];
+    it.each(symbols)("%sName01", async (model) => {
+      const diagnostics = await diagnoseOpenApiFor(
+        `
+        model \`${model}Name01\` { name: string; }
+       `,
+      );
+      expectDiagnostics(diagnostics, [
+        {
+          code: "@typespec/openapi3/invalid-component-fixed-field-key",
+        },
+      ]);
+    });
+  });
+
+  describe("no errors on valid model names", () => {
+    const symbols = [".", "-", "_"];
+    it.each(symbols)("%sName01", async (model) => {
+      const diagnostics = await diagnoseOpenApiFor(
+        `
+        model \`${model}Name01\` { name: string; }
+       `,
+      );
+      expectDiagnostics(diagnostics, []);
+    });
+  });
+
   it("doesn't define anonymous models", async () => {
     const res = await oapiForModel("{ x: int32 }", "");
 
diff --git a/packages/openapi3/test/parameters.test.ts b/packages/openapi3/test/parameters.test.ts
index 4f7454f78a6..d646df97bbb 100644
--- a/packages/openapi3/test/parameters.test.ts
+++ b/packages/openapi3/test/parameters.test.ts
@@ -301,27 +301,32 @@ describe("query parameters", () => {
     ]);
   });
 
-  it("encodes parameter keys in references", async () => {
-    const oapi = await openApiFor(`
-      model Pet extends Pet$Id {
-        name: string;
+  it("errors on invalid parameter keys", async () => {
+    const diagnostics = await diagnoseOpenApiFor(
+      `
+      model Pet {
+        @query()
+        $take?: int32;
+        
+        @query()
+        $top?: int32;
       }
-      model Pet$Id {
-        @path
-        petId: string;
+      @service
+      namespace Endpoints {
+        op list(...Pet): void;
       }
-
-      @route("/Pets")
-      @get()
-      op get(... Pet$Id): Pet;
-      `);
-
-    ok(oapi.paths["/Pets/{petId}"].get);
-    strictEqual(
-      oapi.paths["/Pets/{petId}"].get.parameters[0]["$ref"],
-      "#/components/parameters/Pet%24Id",
+      `,
+      { "omit-unreachable-types": true },
     );
-    strictEqual(oapi.components.parameters["Pet$Id"].name, "petId");
+
+    expectDiagnostics(diagnostics, [
+      {
+        code: "@typespec/openapi3/invalid-component-fixed-field-key",
+      },
+      {
+        code: "@typespec/openapi3/invalid-component-fixed-field-key",
+      },
+    ]);
   });
 
   it("inline spread of parameters from anonymous model", async () => {